[Analysis] 13 Sentinels: Sekigahara Pre-Amnesia Timeline (Spoilers)

06 Apr, 2026

Exploration of Sekigahara Timeline (Pre-Amnesia).

As a child of unknown age. Have absent parents (maybe just clueless and/or working too much?). He meets Shinonome, she takes care of him.
As he told Fuyusaka, in primary school he got confessed to by a girl (maybe more than one? who knows if he was popular...such important info...).
Practiced boxing.
Middle school, before September 2063. At some point, their parents try to separate them, thinking he might have romantic feelings for her and that he could be a bad influence. They were right about him, but Shinonome only saw him as a little brother. In response, Sekigahara starts to rebel against his parents.
Around September 2063. Shinonome starts to date Gouto. "If I date a guy with a good reputation like him, maybe my parents will stop trying to separate us, and Ei-kun will start to be more independent from me and open up to others" was her thought based on extra materials. It worked, and Sekigahara got heartbroken and decided to see her as family, whishing for her happiness only.
Around March 2064 (before graduation), Shinonome breaks up with Gouto after her plan worked. About six months later, in October 2064, Kaiju attacks begin, and they meet Ida and Morimura. Shinonome becomes captivated by Ida and is manipulated by him at school.
At some point in October, Shinonome agrees to pilot a mecha. Sekigahara, worried about her, also agrees.The S2 events seem to happen within just a few weeks or even days. How good Ida is at manipulating Shinonome to get her into that state? They meet after the first wave (as shown in Shinonome’s story), but the timing of these events (6–11) depends on how spaced out the waves are in S2. It also makes me wonder how intense the attack in S4 must have been for all the waves to happen in a single day.
Sekigahara sees Ida and Morimura talking. He shows interested in saving the city (initially didn’t think he cared much about, but he actually does). He agrees to help update the third generation mechas in exchange for Ida to stop using Shinonome. Despite not liking Ida, he ends up being manipulated into distrusting Morimura and starts to see her as suspicious.
He begins updating the mechas and is going to update No. 17. There, he learns that there are logs from 2188 that Miura AI backed up in his mecha before Morimura deleted them. Morimura becomes even more suspicious to him, and he starts to hate her. He promises Miura AI that he will take care of the logs. Miura asks if they are friends before he proceeds with the update, probably to ask him to not go through with it, he ends up not updating No. 17.
Still in October, Shinonome installs DD426 into his mecha after a fight. A wave is approaching.
Same day. The battle goes wrong. An infection occurs, and everyone becomes separated.
Probably on the same day as Event 10, he meets Tomi426 in S1, who says Okino might know how to cure DD426. He gets medicine, but the headaches will eventually lead to amnesia or a vegetative state.
He goes to S5 and finds Okino, trying to ask for help. Okino asks if he knows who caused the infection. Sekigahara seems to know it was Shinonome but refuses to say it, so Okino doesn’t trust him and refuses to help. Hijiyama then chases him.
(Weirdest scene in the game, probably leftovers of unused plot points. I pretend this scene doesn't exist lol) He meets Tamao, who says Okino told her she came from the future and that her parents aren’t her real ones. Then he meets Miura and somehow tells him that Miura AI is from the future and is inside a drone, even though he shouldn’t know that yet (Ida only tells him later). It really breaks immersion. Still, this scene shows him starting to lose patience, unable to trust anyone, and mentally deteriorating. I think it is the moment he starts losing his innocence and moving closer to his past self… pointing guns at everyone
Trigger Hijiyama's route by taking him to S4 while chasing Okino
Goes to S3 and gives medicine to Morimura for the others
Meets Ida. Gets knowledge about loops (which he interprets as different “worlds”) and the existence of another world in 2188. Ida wants to destroy this world to loop. To save himself and Shinonome, Sekigahara agrees to work with him: secure the battle fails and this world get destroyed, retrieving the 2188 logs from Miura AI, and killing Morimura and anyone in the way. He reunites with Miura AI and starts lying to him (with a terrible voice tone in jpn btw, he really sucks at lying). From this point on, he helps search for No. 17, which contains most of the logs.
Around February/March 1985 (Yakushiji was already in S4 in March giving a Yakisoba Pan to Hijiyama). He meets Yakushiji and sees Izumi dying in S3. I don't know why he’s there. Maybe too see the destruction of the sector, look for n°17, or just walking...why not? (ˆᗜˆ)
At some point, he backs up his and Shinonome’s data into Sector 0.
(Unknown Log 1) Records the smug message shown by Android Ida.
(Unknown log 2) Records the prologue message telling his future self to escape this world (loop). Like the other characters, its unclear what he thinks the world is. He doesn’t realize it’s a simulation, but also doesn’t question the existence of looping or time traveling. He probably just didn’t have time to process everything (finding excuses)
(Unknown Log 3) Records the bike log reminding himself to stop Morimura and retrieve the 2188 logs.
In April, Fuyusaka bumps into him and drops her ID. She looks very similar to Morimura, so he starts investigating her. Was he looking for Morimura here?
Still in April, he goes to S2 (his hometown, likely a place he feels safer). Meets and talks with Fuyusaka. Guesses Fuyusaka shares ID with Morimura, meaning they are the same person.He learns she has Morimura’s memories and is gradually becoming her. He hesitates having to kill her. Still suspicious of her, tries to help her. Morimura appears, forcing him to leave.
In the science room, he tries to hack the teleporter locked by Morimura’s ID. The system goes crazy and teleports him, Shinonome, Tomi, and others. To make it more natural it could be that Fuyusaka unlocked it with her voice from afar… though that might make it even more convenient (ˆᗜˆ). This event triggers Tomi’s route.
In S3, he leaves Shinonome behind, who tries to kill him thinking he is 426. He disappears for a few days and later reappears to help Tomi and the others.
In Sector 2, after trying to reach Shinonome, he meets Fuyusaka again and seems still somewhat suspicious of her.
Just before May, Miura AI erases his memories at school. Maybe he ran away from Sekigahara to the girls changing room and erased it. Or he erased it first, then Sekigahara had to hide him there because he couldn't walk with the drone or the drone wasn't obeying him and run away. I don't know. Bumps into Natsuno. This will trigger Natsuno's route
In the background, he was likely still investigating (or stalking) Fuyusaka while searching for Miura AI.
(Unknown Log 4) Possibly recorded after meeting Fuyusaka or after her confession. He confirms she and Morimura share the same ID, and starts to doubt his actions, realizing she might be innocent. Still, he says stopping the Aegis Plan is the right choice.
In early May, he saves Fuyusaka from Wajima. When she asks why, he says it was a coincidence, but she says he's lying. Considering how bad he is at lying, he was probably already watching her. Why? To kill her? To investigate her further? To see if she was anything like Morimura?
She confesses to him. He’s surprised but happy. He accepts her feelings but doesn’t give an answer. He talks about his past with his parents and Shinonome, and says he’s never been confessed to since elementary school. He mentions they are connected by “entanglements” and promises to contact her.
He later meets Takamiya and Miura (now with restored memories) and goes with them to find Natsuno in S2. He hilariously tell them to expect the worst.
Takamiya sees him with Tomi426 body
He finds Tamao426 dismembered. He tells him Miura erased his memories because his plan was discovered. He thinks it’s a trap from Morimura. Tamao426 calls him a nuisance, he shoots him and leaves. From this point on, he loses confidence and enters in his self-loathing phase.
(Unknown Log 5) This refers to only the conversation he had with Miura, begging him to show the 2188 logs. He asks Miura if he really erased his memories because of him. Miura confirms. Sekigahara begs to see the logs Miura had refused to show him and asks him to link them to the current recording. This likely marks the start of his self-hatred phase, especially since everyone (Miura, Morimura, Gouto, 426) already knows about his plan. A walking failure...
(Unknown log 6) This refers to the actual 2188 logs. He watches the 2188 logs and finds out he is the clone of an assassin who was also tasked with killing Morimura. Shippo mentions that he probably saw this, and that it shocked him. Either he watched them here and only processed the shock later, or Miura hadn’t shown them to him yet and only linked the 2188 logs to "Unknown Log 5" later, to show to post-amnesia Sekigahara. The scenes of "Unknown Log 5" (and maybe he watching log 6 too) could have happened when Takamiya finds him in a bad state with headaches. In that moment, he asks her to pass a message to his future self in case he loses his memories, so it was probably recorded around then. (Maybe he didn't get to see the logs from 2188 or maybe he did? How agonizing! lol)
Quit working for Ida, but Ida obviously doesn't know.
At some point, Takamiya finds him in a bad state with headaches. In that moment, he asks her to pass a message to his future self in case he loses his memories. She leaves to save Natsuno.
Hijiyama finds him with Miura AI, sees the 2188 logs, and takes him to Okino. He asks Okino to back up his memories because there are things he doesn't want to forget (what things? His mistakes? Fuyusaka's confession? Shinonome and Miura? Everything in general?) but refuses a personality backup, saying he hates himself and doesn’t want to make the same choices. With this mental state makes sense that the conversation with Miura AI, recorded in the "Unknown log 5", really happened between events 36 and 39. Not sure about if he watched the 2188 logs too.
He takes Fuyusaka to Morimura. In his self-loathing state, he tries to push her away, but they end up having a vulnerable conversation. He reveals the truth about her life and invites her to run away with him and Shinonome. She refuses and chooses to fight. He learns he can’t even run away, because he would no longer be human. He gets even worse. When Fuyusaka tries to encourage him, he says he doesn’t have the courage to choose her and wants to keep running away. In this scene he threatens to kill Morimura, a strange move if he've already watched the 2188 logs (Unknown log 6). At least to me, I doubt he would be pointing that gun to Morimura knowing he was an assassin in the past, unless he was already that self-destructive.
Morimura later calls him to see Shinonome, who has lost her memories. She only remembers him as “Ei-kun” from mecha training. She still chooses to fight thinking of her teacher (Ida).
In mid–late May, Megumi tries to shoot him. He follows her and meets Shippo (426), who explains everything and his plan to fight. Sekigahara refuses to fight and instead asks how to transfer his mecha to someone else (Fuyusaka).
He seems close to breaking down. Unable to save Shinonome, he makes his final decision: he gives his mecha to Fuyusaka, saying it’s better at the hands of someone like her.
Around this point, he likely watches the 2188 logs (if he hasn’t already), breaks down, then inspired by Fuyusaka’s determination, changes his mind and decides to fight for their futures.
Shippo mentions he came to him crying and begging to join the battle. Since DD426 detaches the nanomachines, Sekigahara needs to be shot after the amnesia.
(Unknown phone messages) He records two messages. I remember reading that when you play them, the last one recorded is actually heard first, I don’t have a source for that anymore. The first one we hear has him telling his future self to choose his own path, forget the past, and look for Miura because he has a message for him. The second one tells him to “finish the job.” Initially, I thought that meant killing Ida, but that doesn’t really make sense if his goal was to let his future-self to make his own decisions. I assume the second message was recorded before his change of heart. So I'll believe the person who sid that the messages are played in reverse order. As for why Sekigahara left all these messages… honestly, it was to confuse himself and the player.
He prepares everything for his future self: medicine, Fuyusaka’s ID, keys, and message codes. To avoid Ida finding out, he keeps everything vague and indirect, which makes things more confusing. This is why he confides Morimura the paper and never talks about Ryoko or Fuyusaka in them. Miura AI and Natsuno, Ida already knew them existances.
I don't know why, but he meets Morimura. Maybe Ida lost patience and sent MIB to kill her. I wonder if Morimura have always been chased. Sekigahara seems to be helping her escape or maybe they arranged that meeting. He then questions her actions regarding the logs and and ultimately loses his memories.

Source: Developers Talks in "13 Sentinels: Aegis Rim Official Script Double Strand", this interview and this one too. For the timeline I used my own calculations and this table. Inspired by this blog.　

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