
I've been going through this for days now and hope someone else share their thoughts on this so..the thing between hiragi & chizusumi is confusing me and I've been seeing hiragi in a new light since the last two chapters but again the anigma is chizu so when hiragi confessed to chizu the chapter before the last chizu neither said he loved him back nor expressed any feelings except wanting "to put it in him" quote on quote so like what exactly is the author trying to say , what is their dynamic and is it just about sexual gratification for chizu ? Cause all the other couples had something more deeper and more emotional between them and why is chizu so different as a character from the others and why we haven't had more chapters shading light on him and hiragi's clueless ass (〜 ̄△ ̄)〜

The way I see it, hiiragi had always been watching mafuyu and yuuki, because he idolises yuuki so much to the point he was more interested in yuuki's "perfect" love. Before the current chapter, he never took time to think about his own love, but was mostly watching mafuyu and yuuki's love. He was so focused on yuuki's love that when shizu asked him what does he want to do?he couldn't say anything because he had never given it a thought. All this time hiiragi was chasing the idea of love. And his idea of love is perfect yuuki's perfect love. About shizu, he had experienced nothing but an awful life as a foster child. So when hiiragi took his hand, to shizu, he was like a light in his dark world. That is why he describes hiiragi as "a glittering pebble that he had tucked in a sandbox". Till now there has been only one chapter which focuses on his thoughts. You can learn the way he sees thought hiiragi and mafuyuki in that chaper, I think it was 柊mix_4.
So shizu had been watching hiiragi who was watching yuuki and mafuyu all the time and shizu thinks that hiiragi loves yuuki because every time you see hiiragi, he won't stop talking about him and when yuuki was alive hiiragi just kept idolising him, his eyes were mostly focused on yuuki. That is why shizu is convinced that hiiragi is just feeling lonely now that yuuki is no more. And there is a possibility that shizu thinks that hiiragi is just confused about his feelings for shizu because he had been the only one by his side all along.
You can clearly see that hiiragi had no intention of confessing to shizu, just wanted to continue with the band so that shizu will always be by his side. Hiiragi only confessed because shizu said that he loved yuuki.To prove shizu wrong, he blurted out that he is in love with him!? Hiiragi's abrupt confession and the fact that he always talks about yuuki and mafuyu , wouldn't really make much difference to shizu, who is so convinced about the fact that he can never have hiiragi. There is a clear distinction between loving someone as a romantic /sexual partner and the platonic love which a deep friendship-like bond. That is what shizu is implying. By saying "putting it in" he is making hiiragi aware of the fact that it is NOT going to be the same as their friendship. Shizu clearly wants more than friendship but hiiragi had never given it a thought. He couldn't even say it out loud, it just implies that he had never thought about it
Shizu knows hiiragi better that anyone else and he knows how to make hiiragi think about it. Being the spoiled brat hiiragi is, he always goes to shizu for comfort. Just knowing the fact that there is someone who is always going to be there for him, shizu is like a comfort zone for hiiragi. To get hiiragi out of his comfort, he said harsh words to him. Now that hiiragi is all by himself he is thinking about his feeling for yuuki and shizu. Maybe shizu wanted hiiragi to think about it and that's the only thing he could think of. While cornering hiiragi like that might not have been the best way to handle the situation, it did work for sure. Shizu never experienced being loved in his life. No family by his side. Even in his friend circle, he was like an outsider. That's why he doesn't expect hiiragi to ever return his feelings. Shizu trying to make sure whether hiiragi really loves him, implies that shizu doesn't want to give his everything to hiiragi yet and is holding himselfback which is just another way of shizu to protect himself from further getting hurt.
That's how I interpret it. And in my opinion, shizu is a dark, complex character. We only got one chapter from his POV but I'm interested in him the most.

Dude what you said makes 100% sense to me and I as well was interested in chizu the most since i always found myself drown to quiet gloomy characters but what you said about him thinking he can't have hiragi and that he only confessed to him cause he was feeling lonely made feel sad cause i truly wanted chizu to be loved dearly and i do hope the author give us more insight into both of them too .Thank you for taking the time to reply i truly appreciate it
I'm i the only one who didn't think it would be like this (๑•ㅂ•)و✧ i mean i had a thought or two about how he might be "disciplining" the young master but this is beyond that he's too controlling and he practically moving him like a puppet WTF