These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
And as of Zenia's Arcana Heart 3 ending, it's confirmed they are sisters.
Fridge Horror: Whatever happened to the nuns that were assisting Mildred in Arcana Heart 1? After Mildred is defeated, she gets sucked into the Arcana world, and her floating castle vanishes... either the nuns got sucked in along with her, or it's possible they all died.
Game Breaker: Averted. Konoha's short physique helps her avoid many attacks, but she has a pretty short range.
Played straight with Elsa. Depending on Arcana selection, she has several infinite combos in Arcana Heart 3.
Genius Bonus: Akane Inuwaka's Arcana is named after a type of fox. Knowing that, check out her ears under that do-rag.
Les Yay: Most of the girls have something for another.
Particularly notable with Clarice di Lanza, in that there is no such thing as subtext regarding her fixation with Elsa la Conti.
Mei Fang also seems to have shades of this with her creator. In her Arcana Heart 3 ending, it seems to be more than just shades.
Mildred also, with Fiona.
Moe - The first fully Moe fighting game franchise.
Nightmare Fuel: Lieselotte Achenbach... a cute little kid who's actually a world class assassin Enfant Terrible who carries a doll containing her sister's soul (or so she thought). Uuuhh...
That One Boss: Parace L'Sia in 3's Score Attack, quite possibly the single hardest fighting game boss EVER. Her attacks all come out way too fast and the range on them is too good for their to any reliable way of dodging them and she can easily pull off combos that will deplete your lifebar if she manages to hit you even once! Even her low health doesn't help because her Teleport Spam makes her too hard to hit most of the time, and she slowly recovers health during the fight and actually has a super move the lets her rapidly heal herself. Pretty much the only reliable way to beat her is to try again and again, because the more times you lose to her the less health she starts the fight with.
Viewer Gender Confusion - Raise your hand if you think that had it not been her name and the fact that this is an all-girls fighting game, you might pass up Dorothy Albright as a cute little boy.
The Woobie: Every time Fiona Mayfield loses, she ends up crying and pleading for the opponent to stay away from Mildred.