Shinseiki Evangelion: Ikari Shinji Tantei Nikki

When even a tough dude like his school pal Toji is getting menaced by gangsters, a nice guy like Shinji Ikari feels obliged to seek out the local private eye, Ryoji Kaji, and his striking young assistant, Kaworu Nagisa. Somehow, though, Shinji gets drafted into solving the case himself, with Kaworu's help—although Kaworu quickly proves to be a mystery of his own...

(Source: Dark Horse)