Visting Keiko mother geh.. not a good idea. don't forget that guy is there!! Keiko did slept with her mother boyfriend.
anxious....
Different guy. Mom's boyfriend hits on her (I strongly suspect mom jumps from guy to guy), Keiko is disgusted and calls a guy friend and sleeps with him in a sort of attempt to control her own sexuality and shield herself from older guys who hang around the house.
The guy she sleeps with is part of the high school crew she hangs with. I'm pretty sure he appears in earlier scenes.
In any case Keiko's mom is a piece of work. Or at least has bad choice in men.