I don't have many thoughts about yandere, but I like how john!Rui is a weirdo and I could see them both as being yandere. wendy!Tsukasa getting sick of the stomach when Rui is going out, just the thought of him seeing someone is repulsive, what if someone dares to touch his little brother? Maybe Tsukasa hurts himself so Rui has to stay and take care of him... he obviously tells Rui he should go have fun anyway because the omega is the older sibling, and he knows how to take care of himself. But Rui doesn't mind staying, he loves his older brother so much... Creep. The second Tsukasa falls asleep Rui takes off the omega's pajamas and touches his soft skin, the alpha is so careful taking off his brother's panties and masturbates until he come over Tsukasa's pussy. Of course he steals his older brother's underwear too. How many times does he lick under Tsukasa's ribbon, he can't mark him just yet, but it's enough to keep other alphas away.