Parallels between Mizi and Sua with Sumire Akane
Both Mizi and Sumire grew up in environments where their chance at life was skeptical. Sumire was raised as a sacrifice for her village. Mizi grew up in a world where humanity was viewed as disposable pets by aliens. She witnessed her mother killed in front of her at a young age, and after that, even though she was raised well by her alien parents, always had that feeling of being crushed.
Both Mizi and Sumire desired love and developed close codependent relationships with another from a young age. Sumire with Hakubo, an oni assigned with raising her until she were to be sacrificed, and the only one in her village who would talk with her. Mizi with Sua, a girl who she met when entering Anakt garden.
Both their lovers were outsiders and those easily controlled by others, Hakubo an oni who never felt emotion and did whatever anyone asked him, Sua, a girl broken her surroundings and fear of death instilled in her by her sister who emotionally closed herself off to most for fear of being hurt, avoidant of conflict, leading to her avoiding expressing her pain and who would do as she was ordered.
I think the most notable shared factor between both girls, though, are how they use their relationships with others as a means of control in their lives. Sumire discusses how the reason she takes care of wounded animals is because she likes the feeling of having their life in her hands. For a girl who's known her entore life she will be thrown away for the sake of others, she relishes having the same control over others lives as others have over hers. As well, she longs to have control over those who love her lives after death. She wants them to suffer through grief, to go to hell over her, all so that she won't be forgotten. Mizi, who always felt controlled and crushed before she came to Anakt, also desires control. She joins Alien Stage, knowing the deadly risks, in order to be the one in control. She befriends Sua initially because she adores her frailty, viewing her as no threat. With Sua, she isn't the one being crushed, rather, just like Sumire with her dear critters, Sua is the one under control. Neither Sumire or Mizi actually desire to harm them, rather they relish in the fact that they could if they so wished, just like how Sumire's fellow villagers and the aliens around Mizi can.
Hell, both girls have an intimate scene with their lover where they still think about this. When Hakubo is...um...eating Sumire in order for her to be destroyed by her owns terms, he discusses how he wished he could have been a human and 'gone to hell' for her as she wished, to wish Sumire amusedly replies that he's 'adorable' and that he is in his own personal hell, the hell she longed for him to be in over her. Mizi likewise, in an intimate moment with Sua, calls her 'So adorable' as she is someone she can 'crush', just like how her alien parents, who she felt 'crushed' by, called her. Sumire and Mizi adore their lovers to the point of codependency, they're a scrap of comfort in their scary lives, yet at the same time someone weaker that them who let themself be controlled.
And yet Sumire also has parallels with Sua too.
Both girls grew up in an environment where they had a constant fear of death. Sumire a sacrifice and Sua raised to take part in alien stage, a singing competition in which the loser is killed. Sua had the idea that she was weak and would likely be killed instilled in her by her older sister.
Both were viewed merely as an asset to their family, rather than a person. Sumire was sent away to be raised by Hakubo and was only viewed as a sacrifice by her family. Sua's alien mother Nigeh viewed her primarily as an asset through her singing and looks to benefit her.
Both developed codependent relationships with the one person who they loved from a young agebecause of this. Sumire is rejected by her family and implied to be isolated by the rest of her village, thus becomes attached to Hakubo who is assigned with caring for her. Sua was is implied to have been rejected by some of her 'sisters' for being the 'favourite child' of her alien mother and got her confidence in herself damaged by her older sister as previously mentioned when she was little. This makes her sensitive and withdrawn for fear of getting hurt by others, resulting in her peers nicknaming her an 'ice princess'. Still, Mizi with her sweetness is able to break through her walls, and thus she becomes her main person.
Both girls know they are going to die inevitably, yet longs to be remembered after death. Sumire tells Hakubo that she wants someone to grieve over her, so much that it drives them insane. Sua in her subsong Heart implies in the lines 'Hurt, thats where I wanna fit...Heart, that's where I wanna settle down for good' that she wants to be remembered by Mizi through her love for her after she sacrifices herself, even if it hurts her. Sumire knows she can't escape being made a pawn to be killed in order to stop the village from being overrun by monsters and Sua accepted the fact that she needs to sacrifice herself for Mizi on stage to save her. Despite this, they can't help wishing they'll be remembered through others grief. After all, for two people intentionally raised to be slaughtered, there's no meaning in their life. Yet if somebody misses them, that means there was a point to their existence right?
Finally once Sumire is sacrificed and Sua sacrifices herself for Mizi, grief drives their lovers bloody nuts. Hakubo slaughters most of the village and Mizi destroys the stage, in order to kill her enemies and herself, fueled by the thought that love is only exploitative. Both feel that they should have done something to stop their lovers' death, should've 'taken their hand' when they had the chance. And because they failed to do so, are now left in their own self-inflicted hell. Both Sumire and Sua had similar effects on those around them who they left behind.
In conclusion, Mizi and Sumire complement in each other as being people who desire agency in their lives, to be on top, even if it comes through the hypothetical exploitation of others, while Sua and Sumire and people who long for purpose in an ostensibly meaningless existence.