The reason that people are a little confused why Keita is all over Natori's "playboy" aura is because we skipped over the chapter where he's introduced to Natori through a cellphone image sent by Asako herself. He had a lot of time to stew about it, and then they actually met face to face during a date to the restaurant Keita worked at. Keita was for the most part convinced of Natori's character (but still skeptical despite).
There are a lot of good chapters in the second and third volume, and I really hope more people find a way to read them.