Shintaro is the intro of the manga and probably the anime. He sat next to Ayano in school. He was stoic and smart, but didn't really care about anything. He didn't have dreams or fantasies and thought he figured the world out. Without realizing, he spent a lot of time with Ayano an she was unconsciously a big part of his life. He thought he had nothing but in reality she ment a lot to him. When Ayano died, he realized that without her he truly had nothing. He became a neet and locked himself in his room. After a year of being a neet, he met Ene. A year after he met Ene, he went outside to get a new computer (because he because addicted to the internet and Ene caused him to break his computer). He got involved in terrorism at the mall and eventually joined the Mekakushi Dan. There two views on how he got there, but apparently he get's a near death experience while either being suiciadal over Ayano or trying to save Haruka (Konoha before he lost his memory and became a cyborg). When he enters the purgatory realm, he meets Azami and Ayano. He fixes things with Ayano, and gains eye powers. She passes her powers to him. He used to be stoic, but now his personality is cool/cold and there's times where he becomes kind. It's complicated. He's in a long of songs, but his main songs are Lost time memory and Toumei answer.
Momo is Shintaros imoutou. She has the eye ability to gain attention. When she was small, she almost drowned. The near death experience gave her that ability so that someone would notice her and save her. She became an idol using that abiliy, singing songs and rarely being in tv shows. She's extremely famous even though she doesn't like acting. She joins the Mekakushi Dan after she quits show business and Kido finds her in an alley. She hasn't learned how to control her eye powers though, so she usually sticks to Kido, but when they need her the eye ability comes through. She's in a few songs, but her main song is Kisaragi attention.