uke's sister introduces him to her Mr. Perfect boyfriend, who rings sirens in his mind. he ends up getting close to the guy, forgetting the red flags. later their life is turned around after they get conned by him. though daichi is already too in-love with tatsumi to try to forget him.
to be honest, daichi should've moved on and tatsumi should've lived a better life with daichi in mind. wouldve been better if tatsumi died ngl.
Hitsuji no Kawa wo Kita Kemono