on the surface, Dazai and Chuuya could not any more different. where Dazai is calculating, Chuuya is capricious. where Chuuya is compassionate, Dazai is cold. put a hot-head and a melancholic together and you get a stalemate, a dead-end, a full stop. just throw it all away and start over. but by some miracle, the union that is Soukoku holds the potential to overcome any adversary precisely because of these apparent differences— and the undercurrent of strong similarities.
Soukoku grew up alone. as shown above, whether the capability is mental or physical, power isolates its holder. this is especially evident when surrounded by other people, situations where the potential for connection is abundant yet something invisible precludes it. failing the establishment of normal relationships, both Dazai and Chuuya placed themselves at odds with society. they were different. they were misunderstood. no one could possibly understand their feelings... except the other?
nihilist Dazai's anhedonia manifests as suicidal depression and bleeds into needless cruelty, looking for self-actualisation in sadism. indestructible Chuuya relishes an all-out brawl, desperate to be pushed to his limit and fear death for the first time. neither find much success here. though the small victories sustain them for some time, there is no meaningful progress. Dazai squanders another day. Arahabaki stays trapped in its shell. this too is isolating simply for the intimacy required to explain it all.
more than anything, what they need is a challenge.
when choosing romantic partners, we look for people who will hurt us in the right ways, reenacting our childhood experience of love with all its traumas. Soukoku is no exception. Chuuya needs someone to manipulate him and depend on his strength, someone who feels close like family but changes his mind on a whim and disappears. diagnosing Dazai, whose past remains a mystery, is much more difficult. still, i'd argue his need for someone protective and giving, stubbornly accepting all his violence with spiteful forgiveness.