Uhhh extra chapters are just bonus content that the main story didn't get to there's no rule that it's "only sex". There's not even a guarantee it'll be about the main characters!
6.5 is literally about the whole family eventually wearing matching clothes lol
but yeah, shouji is probably the dad but ririko would definitely choose sentarou to rely on ... i mean, he was definitely the most decent of the three lol
Damn what a ride. Nice one! The buildup, the plot, everything coming together with a click… I did think the beginning was ridiculous but as I read along it started making sense. That was super nice!