Houyou Jikken
Kinda funky pacing. Chunks of time were skipped, which took away from the potential to really get you in the heart, but the art was nice and who am I to tell you that you can't sleep with your fictional cousin. The story: University student Miya lives with an incurable disease that will likely kill him in his early 20s. He spots a flashy man in the university's library one afternoon and is surprised to discover the man, Rei, is actually his cousin who used to visit him in the hospital as children. But even more surprising is that Rei has an interest in biology and in Miya's disease, which he claims to be able to cure.
Koisuru Cupid
A ghost can't rest in peace because of unfulfilled business, so he asks his best friend to confess on his behalf to a man he'd admired from afar. Lawyers who use lawyer-speak in bed. Cousins who look so similar they're mistaken for twins. After a misunderstanding, they get a lil closer than most first cousins do.
Fuyushirazu no Koi
A boy sees his mother cry for the second time when she catches him about to kiss his sleeping cousin, who often crawls through his window to borrow his air conditioning. This is a gentle story about mutual love, and there is the thread of a story about parental acceptance. In the end, the mother reminds them to use a blanket in the cooling weather, indicating she knows they're going to sleep together - and while this doesn't indicate approval, per se, it shows her acceptance. While it was sweet of the scanlation team to take the effort, they duplicated many pages in this with colorized versions, which are distracting to some readers. Head's up if that bugs you.
Osananajimi wa boku no hero!
Nao has a history of men attacking him and is protected by his first-cousin who is also in love with him. This is the second "I'm in love with my cousin" story I've run across today.
Tone