I remember that the seme and uke here has both tattooed rings imprinted on their ring finger. The uke is a writer and woke up naked (?). So I'm assuming they had sex. The seme here has some kind of a mental disorder... his personality fluctuates and can be both affectionate and abusive to the uke. Some time later, the uke rejected the seme and the seme here went back to the psychiatry ward (?) Anyways, the uke found out that the seme grew up in an area full of opium so that kinda explains why he has mental disorder. So the uke regretting his actions decided to go and take back the seme.

Hanazono no Kioku by Hino Garasu ?

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Yup! That's exactly the manga that I have been trying to look for. Thank you so much!