Supernova is a shotgun pretending to be a handgun to go along with her shipmate GSh-18. She’s one of the most supportive shotguns available and she enables some real dumb stuff. You want to use MGs at night? Well, her skill allows for that. Do you need a little more defensive capability for your shotguns? She brings that too, all in a kancolle-flavoured package. Honestly, she’s not an automatic pick on every team. You’re likely going to have to drop a MG in your formation to make use of her fully, which can be an issue.

Her two main draws are her movement speed and her MG buffs. Her roller skates allow her to go almost as fast as a handgun, but not quite. Not much else to say about that, but main reason to take her is the MG buffs she provides.

While crit rate is nice, the accuracy buff she provides to MGs is fixed. This means that MGs are entirely usable at night. It bypasses the accuracy penalty that you would normally have with no PEQ. While not the most relevant thing currently, you definitely want to have Supernova in your back pocket for the future.

Stechkin's base version already got a pass for being usable.

Her mod gives a slight increase in her capabilities buff-wise. Her passive basically tries to turn her into a sorta-DPS to go with her buffs to allies, but TBH you'd be fine leaving it at the slight increase in power Mod 1 gives.

Props for accuracy. She spends the animoo's story just living in the dorms and only coming out for tests or really weird situations where they cant spare bodies, and she's basically the same in the game - she'll be in your dorms a whole lot. She also has three unique items that affect her passive but otherwise all do the exact same thing. She isn't completely useless, but there's not much reason to pick her over other MGs that don't have finnicky mechanics, because you frankly will not need that many MGs anymore.