It is very cute. The Main character is a bit stupid actually having Sex with his brother without clearing up their feelings. The mc is very lewd and obviously loves his brother romanticaly but he just doesn't notice it. The plot is alright but it's not the best and the part where his classmate shows up is unsatisfary. Way to short. He just gets briefly introduced and then he never appears again.
3-pun Instant no Chinmoku