The main protagonist of the manga and brother of Momo Kisaragi, Shintarou is a hikikomori and as such, he has a hard time dealing with people. He seems to be constantly bothered by Ene.

First appeared in Jinzou Enemy. A hikikomori (recluse/shut-in) young man with an IQ of 168. In middle school and high school, before he was a hikikomori, he performed at the top of his class in National Mock Examinations. He is no longer in school. After dropping out, a mysterious software enters into his computer named "Ene," and, being unable to control her actions, his lifestyle is at a loss. Due to one of Ene's pranks, his computer breaks down, so both Ene and him go to the department store for shopping where they happen upon a group of terrorists. They end up stopping them together with the Mekakushi Dan. After this, he and Ene come to join the Mekakushi Dan.