100% Dazai is the clingiest most physically demanding boy to be close with but, also is terrified of being touched, hugged or cuddled because he has never had that before. If he wanted a hug there was no one to hug for his whole childhood until Chuuya came a long but even then how is he supposed to communicate he wants human contact? He refuses to be weak enough to appear hurt and he won't touch Mori or any other older member of the mafia since it is a risk so he has no experience other than being hit or kicked. So he just doesn't seek the physical affection he craves and just protects himself. Dazai also felt that perhaps he was dangerous to touch, his ability posed risks to others and he worried that was why no one ever held him, he must have been doing something wrong after all
Years later he still doesn't quite understand it, when Atsushi hugs him he still finds himself going stiff waiting for the pain and when Chuuya comes near him he is immediately on the defensive even if he trusts his friend with his life he doesn't trust the friendly affection. Dazai despises this unsettled feeling he gets when this craving for affection is filled, he doesn't know how to react or what to say. It is like this until Kunikida, while Kunikida can be rough with him when he is soft the other doesn't expect reciprocation and realizes when he is overwhelmed and backs off but the offer is still there, he feels safe laying against Kunikida on the train and in the car during long rides.
Kunikida is surprisingly patient with him and never uses these affectionate movements to change them into harmful traps, Dazai feels reintroduced to learning how touch works. He can hug Atsushi back (somewhat, its still a work in progress) and Chuuya is still rejected but the redhead notices a change in Dazai's reaction to general contact, he isn't as off put by it and he notices that his former partner clings to his new partner rather often. The two are noticeably closer and Dazai is always holding onto Kunikida with a smile on his face.
When Dazai and Kunikida officially fall for each other the two are almost inseparable, Dazai refuses to let go and Kunikida is soft for the attention knowing how long it took to get this far so he tolerates it with a soft flush and faux annoyance although he will actively ignore the teasing remarks as to why he isn't dragging the brunette off, and when they are alone Dazai drapes himself over Kunikida and just wants to be as close as physically possible, clinging like a koala and nestled up like he is desperate for Kunikida's body heat and will in fact die without it.
Chuuya noticed the two were in love before anyone else and that was fair due to the countless years he has known Dazai and this was the first time he had seen the bandaged man desperately fall in love, he thought it was kind of adorable and he found it amusing. It was all too tempting to torment Akutagawa about how hard his former mentor had fallen for Kunikida of all people but he resisted opting to wait for the oblivious kid to finally realize it on his own. Chuuya eventually got to the point that he could touch Dazai's shoulder without recoil and Akutagawa was extremely jealous, he wanted the attention and affection too! Some day he would definitely get a hug, he was determined after seeing Atsushi get one.
I feel like the first time Chuuya ever tried to hug Dazai (perhaps after seeing Dazai become unsettled) that Dazai just freaked out and left as fast as he could, then proceeded to ignore and avoid Chuuya for like a week. He doesn't get how Chuuya could so easily hold him like that when obviously something was wrong with him (even if it was just in his head) and poor Chuuya had to see his only friend literally breakdown and avoid him because he tried to hug him once and is very confused. Chuuya sees it as a comfort and safe thing but for Dazai he wants and craves it but is terrified he will just get hurt instead.
Also Kunikida hugging Dazai after a tough case where Dazai could have died and just bawling over how scared he was for him, Dazai finally realizes Kunikida won't hurt him like this and he is safe and man just looses all tension to the point Kunikida freaks out thinking he broke Dazai by just holding him while Dazai having no idea what to do but wanting to stay like this is just limp and safe in Kunikida's arms. He is like a ferret, wiggly, limp and snuggly.
If this is bad blame it on my 2 hrs of sleep ok
