>>49620548
Twinning, but it's just an anon becoming one of Hecatia's bodies after she misplaces one. He has control when she's not using it, but he'll be possessed by her from time to time and start subconsciously picking up more of her mannerisms each time it happens.

>>49577097
>This would require clone, wouldn't it?
Not really. In Banki's case, it's unclear whether the head can think independently. In my headcanon, she can create a temporary personality for it and enjoy her time.
>Kogasa making out with her umbrella.
Not a selfcest.