@Rozzak
Mayu's cousin and her boyfriend from way, way back... in chapter 2.
When this series finishes I'll probably make an infographic with all the characters to show all the storylines and how they're related.
@muge - Yes, an infographic about these characters might be certainly helpful. Thanks and sorry for all the trouble.
I certainly feel like Shimura could have done way better for these characters (Mayu's cousin and her bf) way back when and not 4 or 3 chapters before the series is ending... the plot of this chapter feels like it was somewhat cramped and rushed. And too simplified for such a thing like this :/c. Then again, iirc, Mayu's cousin was very impulsive so, I guess... yeah... At least she didn't end up with her mom's bf and the guy was honest with her about that, too.