We get a initial glimpse of the Okita vs Nobu fight, ending in a big, devastating explosion, followed by a reveal that the Nobu vs Okita battle was actually the LN the protag was reading until he got a phone call from his mom.
Later protag goes to watch TV and the news are making a special anniversary coverage of the big cause-unknown explosion that happened in Teito in 1945, the same explosion that got explained away as a Servant battle in the LN. He gets a call from the friend who lend him the LN asking if he liked it. Akagi tries to pretend he liked the story but it was clear he wasn't a fan. The friend asks if Akagi can still do the cool magic trick he did as a kid, which is pretending to drop food but actually make it float in the air. As the friend asks this, Akagi drops his glass of water but manages to catch all the water back into the cup before it falls to the floor. All while telling his friend that he forgot how to do the trick.
We get Akagi's backstory explaining that the only Magecraft he can use is slowing down the movement of any object he touches. He was just suddenly able to do that one day. No one ever taught him Magecraft. Despite this, his estranged father says he has no talent as a mage. In the flashback scene, we see 6-year Akagi and his dad in a hospital, in front of Akagi's grandmother bed. Dad orders Akagi to never use Magecraft in front of people and warns him that mages can never have a happy life. Only the father side of Akagi's family was a mage family. When his mage grandma was young, an accident made her unable to walk, so she stopped interact with people an started dedicating 100% of her time to her magecraft research. She didn't pass her magecraft to his dad, so RIP mage family. Dad married a muggle woman, the divorced a few years ago due to job problems. Kanata Akagi is not interested in Magecraft/mage stuff nor tries to do greater things with his cool slow down skill. He believes it's wiser and easier to just live a normal, peacefully away from that. And thankfullly he lives is the one era that would allow that.
Cut to Kanata meeting his dad for the first time in 6 months. Kanata doesn't look too confortable with having to meet his dad twice per year. Instead of going to a café like in all other meetings, this time dad decides to pay Kanata to help him clean up late grandma's belongings. They go to grandma's abandoned villa. Dad sucks at mana detection, so he called Kanata to identify what are the Mystic Codes he needs to get rid of. Though he tells Kanata that he can pocket that he feels like he can sell for a good price (but not activate any Mystic Code under any circumstances).
Kanata looks through some books, then finds a weird hourglass, but he can't tell if it's a Mystic Code because he also sucks at mana detection. He checks a new message he got on his phone, causing him to drop the hourglass, but he notices and catches it before it hits the floor. Of course, he had to use his Magecraft for that, meaning he passed mana through the Mystic Code, therefore activated it, just like dad told him not to. The sand in the hourglass begins to drop. He gets a phone call from Taka, the friend with the Okita vs Nobu LN. Taka starts saying the exactly same stuff he said in the previous call. Then he gets the exact same call he got from his mom earlier in the morning. He looks at the window and sees the sun quickly rising and setting backwards. He realizes what's going on and looks at the clock, which is also going backwards super fast.
He grabs the hourglass again to look for a way to stopped in but he's absorbed and sent somewhere. He wakes up inside a train, in front of girl protag and huge armor guy. Girl protag decides to ask questions later and tells him to evacuate to another wagon first. Guy in military uniform sitting on one of the train's bench tells Lancer that it's ok to kill both of them. Akagi is to dense to run, so she grabs his wrist and runs with him, dropping some mist vials behind as she does. She deduced that Akagi is not on Lancer's team since it was ok to stab him and that Akagi is a mage because he randomly appeared out of thin air in the middle of a Servant fight. She explains what a Servant is and that the only way of fight is summoning their own Servant. She opens her suitcase and lays out the materials to summon Saber: a cloth with her magical and Avalon. She starts doing her chant, but Akagi pushes out of the way because Lancer reached them.
Lancer's attack destroys Akagi's backpack, causing the Okita vs Nobu light novel to fall on top of the magic circle as a catalyst. Okita is summoned. The Command Spells are in Akagi's hand. The girl is expectedly pissed that he stole her Saber. Lancer tries to name himself but Okita cuts him down and calls him and idiot for it before he can. He just says he's a Gert Krieger. After Lancer is defeated, Okita does the "Are you my Master" scene.
After they get their moment, the girl interrupt to ask the basic questions of who Akagi is, complain about her stolen Saber and asks if he understand the implications of being a Master. Before anyone can answer anything, Okita notices Nobu's presence. The two protags run away while Akagi asks what year they are in. She answers Teito 1945, confirmed his suspicions that he went 75 years back in time and that his LN was non-fiction. End of chapter.
Now he's going into the Grail War, with the nice advantage of already knowing all the characters and some of the events beforehand due to the light novel.