i feel like the ALSTG fandom puts too much emphasis on how toxic Mizisua is and tends to forget WHY they are so toxic: they love each other. it's a messed up and unhealthy kind of love, but it's love.
in this world where they were never meant to be, where they are nothing more than disposable pets, having someone reciprocate your love and dedication is almost the best thing that could happen. but of course, those circumstances lead to a lot of bad things.
SUA is extremely possessive, submissive, dependable and obsessive towards MIZI. she doesn't let other kids play with her (that one comic w Ivan), she forgives her for anything she does (when she slapped her, both zomstg and alstg; when she calls her "adorable"), will do anything she asks her to (swapping dresses after MIZI suggested so despite not liking white dresses), and so on. that's because she's afraid of losing her in a paranoid level. as i've seen someone say: MIZI is SUA's reason to live, the oxygen in her lungs and the blood in her veins. she's her God and her universe. this obsession makes her dismiss not only her own feelings, but also MIZI's - killing herself so MIZI has to carry the grief, loneliness and survivor guilt instead of her in ALSTG, SAing her in ZOMSTG...
MIZI lashes her anger at SUA and has controlative behaviors towards her* (despite feeling guilty for both, because again, they love each other), as a way to regain the agency/autonomy the aliens will never give her and she craves for. behavior that SUA allows and legitimates - they have opposite coping mechanisms and that makes them perfect to (be) each other('s punching bags). SUA is her safe space, her partner, her best friend. they share everything, every moment, every pain and every joy. both of them need that - way too desperately for their relationship to work out.
*dragging SUA along on MIZI's own dreams, again slapping her/calling her "adorable" like Shine used to call her, deciding things for her etc. besides she also tried to kill herself at some point, knowing SUA couldn't live without her.
but despite all that, they love each other and they care for each other. MIZI cries after slapping SUA. SUA looks terrified when she finds MIZI with her face hurt. yes, they do a lot of wrong things, they hurt each other and should be held accountable for that. but, as MIZI herself said, despite everything, "it was love". something both were desperate for and were very lucky to find.
their relationship is beautiful in a tragic way.
