Summary of Mizunashi Rena, Hondo Eisuke Arch

Hondo Hidemi and her father, Hondo Ethan, were CIA agents who were posing as members of the black orginization in order to gain information on them. In order to protect Hidemi, Ethan killed himself, and they had to make the orginization think that Hidemi did it. In order to keep her brother safe, he wasn't told anything, and Hidemi began posing as Mizunashi Rena, a TV announcer. Hondo Eisuke her brother began searching for his sister and suspecting that Mizunashi Rena had killed her (not realizing that actually was her). He starts asking Mouri questions to try to get information to help him figure it out.(Actually, at first, he also thought that Kogoro might even be working with the black organization and hiding his sister) While Rena asked Mouri to keep an eye on Eisuke (Mouri doesn't know very much about the situation though).
During a confrontation with the black orginization, Rena, code name Kir, has an accident and is unconscious for a while. At that point, unsure of her identity, the FBI keeps her secretly at a hospital, while Eisuke and the black orginization are both searching for her.
Conan, the FBI and Eisuke eventually find out the truth of the situation, and when Rena regains consciousness, the FBI ask her to return to posing as a member of the black orginization in order to keep gaining information about them.

At the  end of the next case though. Rena is forced to prove her loyalty by killing Shuichi. Shuichi and Conan anticipated this and set up plan to fake Shuichi's death. A low ranking spy with the black organization killed himself in the last case. He also touched Conan's phone. So, they put his body in Shuichi's place. There's will be a body, found with a bullet hole in his head (because he shot himself) and his finger prints will be on Conan's phone, where Shuichi's should be. (but he covered his fingertips with glue in advance to hide his prints) Rena shoots Shuichi (Blood shoots out via a device made by Agasa) and blows up the truck with Rikumichi (the spy who killed himself) inside, and Shuichi escapes in Rena's car. Thus keeping the trust of the black orginization.

The FBI also think that Shuichi is really dead, except for James Black who noticed Shuichi's fingers, so they had to tell him.

Eisuke says he is moving to America because he wants to one day become part of the C.I.A like his sister and father.
Also, it is revealed that his reasons for apparently watching Conan suspiciously in the past were because he all along suspected that he might be Kudo Shinichi, and in the end, lures the truth out of Conan by saying he wants to take Ran to America with him because he has a crush on her. Conan has no choice but to tell him he is Shinichi.