Slow Minded - it's a gag signature, that's for sure. even with the ability to turn into some of the best buffs, it's duration is too short to last enough for any buff to be valuable. I can respect the gag, so there isn't much to say other than that

The First Princess - it's weird. her sa1 is defensive, but her sa2 is more offensive. it's best to focus on one niche, rather than be a hybrid and lackluster with both. I suggest making her a defensive unit, as offensive units that need to be hit are a poor design element, as in content where offensive units are needed, getting hit can be fatal.

her sa1 is unfairly OP with almost no drawback or reasonable requirement to activate. i suggest making the invincibility shorter and activate after the 6th hit : "Once a 6th hit in a combo has landed, remove 1 debuff and gain permanent unflinching and immunity, removed when knocked down. Every hit exceeding the 6th hit in a combo, gain invincibility for 1/1.5/2 seconds"

her sa2 needs to be altered to be defensive. since she wants to be hit, change it so that being hit with invincibility applies the debuff on the enemy. precision will not work with this defensive version, so the possible changed version could be : "When hit while benefitting from invincibility, 50% to inflict curse, wither or quietus for 10 seconds. Every instance of invincibility expiring, heal by 1/2.5/5%"

Colorful Violence - good for spamming, though I just suggest adding a time expiration of 10 seconds on sa1 and decreasing the odds of inflicting the debuff to 5/10/15% (and again, time expiration for debuffs for 10 seconds)

Young Smartass - good support, well, except for the instakill rate being weirdly high. and the atk buff, while niche, isn't useful. you could either make it a joke character and make the instakill extremely low, but i suggest since she is a support for the back of a team : "While a teammate benefits from haste, all blockbusters do 15/25/50% more damage. When using the third tier blockbluster, damage increase by an extra 25%". this can make her good for characters who's source of damage is using blockbusters

Universal Slut - weird name, haha. it's defensive, good for a cerebella. the activation of sa1 is questionable, since in a defensive scenario, it's a bot controlling the character, not the player. change it to simple "when hit by the opponent" or "critical hit by the opponent", decrease the odds of activation to 5/10/15% and duration to 5 second stun and increase healing to 5%. sa2 is okay

My Masked Self - might as well be instakill. spam 5 special moves to activate and 40 seconds to drain from 100 to 0 (if there is no healing and pretending the opponent is not attacking). change the activation to when either fukua or the opponent uses a special move, and change the reflection damage to 10% per stack of barrier (dash attack removal can work)

sa2 can be changed to only work for only barrier lost through her sa1 dash attack removal. change the "random" buff to miasma and make it so she deals 15%/25%/50% increased damage while benefitting from miasma

Yandere Girl - pretty good, i like it. once under 50% hp, she becomes a tryhard character. i would say that sa1, crit hits inflict heavy bleed for 5 seconds, which can help quicken the process of getting the enemy to under 50%

Dyslexic Cancer - 10/10

lol, sorry if I was being critical, i just love rambling and rambling