Eisuke comes in 508 chapters into the story, as a transfer student into Ran and Sonoko’s high school class. He’s apparently a fan of Mouri Kogoro, and wants to follow the detective around for a while and help him out on cases. Promptly trips over/runs into everything ever. Notices that Conan is standing next to Mouri-tantei while the detective is “sleeping”.
Chapter 530 - Ran, Sonoko, Conan, and Eisuke are going to stay at one of Sonoko’s family villas (which for some reason requires hiking through the woods with Eisuke carrying all the luggage because he keeps losing at jan-ken-pon). The bridge to the villa is down, so they wander over to a nearby house to use the phone. And because Conan is with them, there is a murder. Murder gets solved, Eisuke is suspicious of Conan.
Chapter 550 - FBI agents talking about the Black Org member/TV news host (Mizunashi Rena/Kir) who is in a coma under their care. Switch to the Mouri Detective agency, where the famed detective is griping about his cases and lack thereof. Eisuke was there watching, but apparently he is Canada is a ninja is pretty good at being unnoticeable, at least enough to freak Conan out a bit (and get coffee poured on him, and have a door opened into him despite the giant window in said door). There’s a conversation between Eisuke and Ran about TV personalities and manga authors taking breaks. Eisuke mentions someone on TV who’s gone missing recently. This of course leads into another case (though not the one Eisuke was thinking of). Rock star is found floating in river. The only witness is a young boy. Eisuke decides the boy is telling the truth about what he saw by using the same trick Mizunashi Rena used on Conan (checking pulse and breathing rate, monitoring pupil dilation and other reactions). Suspicious Conan is suspicious. And let’s solve a murder now! Yay! Eisuke’s clumsiness is helpful here when he “accidently” takes a picture of a photo album containing pictures of the suspects. They’re having trouble solving the case, and Eisuke has this odd little shiny-glasses-of-frustration/anger moment. Suspicious Conan is still suspicious. They eventually do solve the murder. On the car ride back, Eisuke starts asking questions about cases Mouri has solved for/involving famous people. Suspicious Conan is so suspicious.
Chapter 553 - Since the last series opened with the FBI agents discussing Kir, this one has to start with the BO members discussing her. Apparently, she’s pretty impressive and dangerous. Even Gin thinks she’s trustworthy. Cut to Café Poirot. Apparently, it’s a weekend morning thing for Mouri, Conan, and Ran to go and get coffee. And for some reason, Eisuke is there too. At seven in the morning. Because apparently, he saw something interesting on someone’s blog which reminded him of the Sherlock Holmes’ story The Red-Headed League. Everyone thinks that it might be worth looking in to. Then Eisuke mentions where the person lives, and suspicious Conan is suspicious. Mostly because that neighborhood is where Mizunashi Rena crashed her motorcycle and was taken by the FBI to the hospital. Oh. Look. Another murder case, which happens to be partially related to the job that Eisuke had mentioned earlier. Eisuke leaves, after asking a lot of questions about Mizunashi Rena’s accident. Cut back to Gin and Vodka in their fancy car of evil, and Gin recalling the family name of the man Kir murdered. Hondou.
Chapter 556 - Eisuke doesn’t actually appear in this case, but Conan, Haibara, and Agasa discuss him. Conan explains that he thinks Eisuke’s not one of the BO, mostly because during the case in chapter 550, Eisuke’s shiny glasses moment involved Eisuke crying tears of frustration. Which in Conan-logic automatically means he’s not a bad guy.
Chapter 582 - Ran and Sonoko discuss Eisuke’s recent habit of going home straight after school. Suspicious Conan is (surprise) suspicious and decides that Eisuke is most likey looking around hospitals for Mizunashi Rena. Hattori and Conan discuss Eisuke. Apparently, Eisuke’s father worked with lots of foreigners who wore lots of black clothing and hated to have their pictures taken. Conan, Haibara, and Agasa go to meet with a person who has a picture of and information on Eisuke’s father. All the information that they get is mostly things people overheard, and the main piece of information is that Eisuke’s father worked for “the company”.
Chapter 585 - Hattori and Conan discuss Eisuke. Ran, Sonoko, and Conan go to the hospital to visit a friend of the girls, and run into Eisuke there. Eisuke is showing a picture of his sister to nurses, and asking if they’ve ever seen her. Surprise, surprise, said sister looks exactly like Mizunashi Rena, although Eisuke insists they’re not the same person. His sister left home ten years ago, and Eisuke is trying to find her. Ran suggests that they go and meet up with a friend of her father’s, who is a big fan of the TV personality. Of course, there’s a case. Case gets solved rather quickly. They watch a video of when Mizunashi Rena became popular, due to her decision to donate blood during an accident. Eisuke is insistant that she’s not his sister. Conan agrees, because Eisuke has type O blood, and Mizunashi Rena has type AB.
Chapter 587 - Mouri, Ran, Conan, and Eisuke go to solve a case at the house where Eisuke’s mother worked as a housekeeper. Eisuke does in fact have type O blood, there’s a rather awkward moment when someone calls Ran Eisuke’s girlfriend. Also, Eisuke has a scar in the center of his chest. Startled Conan is startled and perhaps has figured something out.
Chapter 595 through 604 - Eisuke’s gone pretty much missing since the start of winter vacation. Apparently, he found a clue at the hospital where they’re keeping Mizunishi Rena, although, nothing about his sister, just a member of his father’s company. Said company is the CIA, and Eisuke’s father was a CIA agent, who was murdered by Kir. Unfortunately, it turns out that Eisuke hadn’t found a CIA agent, but a member of the Organization, which Eisuke’s father had infiltrated before his death. Lots and lots of stuff happens, mostly complicated things involving FBI, Conan, and the Organization, also bombs and
Xanatos speed chess. It turns out that Mizunashi Rena really is Eisuke’s sister, and a CIA agent, and that Eisuke’s bloodtype really is AB, thanks to a bone marrow transplant. Eisuke attempts to ask questions and figure out what’s going on, but he gets hustled out of the room by a FBI agent, and disappears from that particular story arc.
Chapter 619 - Eisuke, Ran, Sonoko, and Conan go to karaoke, to celebrate Eisuke’s return to school after being “sick” for a while (unknown what he actually did during this time, other than get a bit more information about his sister and the CIA, and refusing the Witness Protection Program). They’re at karaoke, and Eisuke vanishes for a bit, then comes back, pretty much having a panic attack. Suddenly, a murder is discovered! And it was the guy that was following them! What a horrible time to look suspicious, Eisuke! Conan thinks that Eisuke is possibly the murderer, since the victim (a possible FBI agent) was trailing Eisuke, and apparently, Eisuke is impulsive enough to murder an FBI agent who was keeping track of him. Turns out that no, it wasn’t Eisuke, no, the guy wasn’t an FBI agent, and Eisuke’s freak out of epic proportions? Because he thought he saw two guys making out. Then Eisuke walks Conan home, tells Conan that he’s in love with Ran, tells Conan that he knew all along that Edogawa Conan=Kudo Shinichi, and tells Conan that he’s going to move to the USA and become a CIA agent.
The end.