 If you liked
Aoi Bungaku Series
|
 ...then you might like
Nomad: Megalo Box 2
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(This recommendation is mostly for the No Longer Human part of Aoi Bungaku Series)
In both, the protagonist deals with a grief/psychological troubles and gets addicted to drugs/"medicine", an addiction which makes him spiral further into despair, althrough some other characters are trying to help him.