I just love how these three guys are involved in romances of increasing difficulty like a game: Easy mode (Seto), Normal mode (Inuyama) and Hard mode (Tokio).
Yeah, Seto is on easy mode. It's just that Seto himself is the biggest obstacle to his romance, considering how much effort Anjou has had to go through to get him to develop to this level from when the manga began.
That makes it the opposite for the girls: Anjou on Hard mode, Toyoda on Normal mode and Chii on Easy mode (if she ever wanted to, but I'm not seeing signs of that).
I've never head of "Hanahaki" before, but that Wiktionary link shared by someone is pretty interesting. I thought it was another term for
BSS (a.k.a "NTR-lite" due to no established romantic relationship, or just good 'ol painful jealousy), but turned out to be different.