Responses
That’s where I don’t agree with the use part. Shira offered his helped. The night of the bond he explained to him why he is going this route, he didn’t force him and he was being honest. He didn’t manipulate his feelings and he would have totally accepted if shira agreed not to do it. But they both consented (〜 ̄△ ̄)〜

Why a lot of people hate Sumi? I know that he did something that hurt Utou, but you know what? Utou was a coward, he didn't say his feelings when was the right chance, he knew the other guy had bad intentions against Sumi and didn't warn him, he pried in Sumi's personal info but didn't try ti talk with him nor make a real (emocional) bond with him
And there's also what the other Omega said to Sumi about "don't destroy Utou", Sumi couldn't avoid to think that he was causing trouble to Utou, and he didn't want to be a burden to The one who was kind to him
Sumi felt that he had nothing, that he couldn't keep depending on Utou anymore, and everything was too exahusting. He was being stupid, inmature and selfish, but can you really blame him?