Gladly.

This is Koyomi! That's the sort of "magical girl" I meant, btw -- kind of old-fashioned fairy tale rather than Sailor Moon. If you're looking for a more mahou shoujo genre thing, Mayu is better for that. I can ramble about her too if you want!

Anyway, Koyomi is adorable. She can come across as a weak character since her actress had some scheduling hiccups early on in the series, but she's pretty great once you take a closer look.

After an event that led to the birth of many monsters and gave the main character, Haruto, his magic powers, she showed up with no memory and with some sort of condition that led to her requiring infusions of magical energy. She doesn't know who she is or where she came from, but Haruto has given her hope for the future (Haruto giving people hope is basically What The Series Is About). She starts the series off as a very cold person, wanting nothing to do with anyone but Haruto, but she manages to grow and evolve and become a more open, kind person who cares about others. Which is one of my favorite character types ever. (She's really similar to Philip from Double, who I adore for the same reasons.)

Where she really shines is the end of the series, when the mystery behind her identity is revealed and she gets to react to that. Spoilers ahead: She's actually a magically-created homunculus of a girl who died years ago. Her father, the villain of the series, is trying to sacrifice countless people just to fully revive her as more than the shell that she currently is. Her condition deteriorates and she dies, but not before accepting her fate and insisting that nobody should ever hurt anyone for her sake again. Which may not sound like much, but it's a very refreshing twist on a theme that the Weird Mystical Deuteragonists from the past three Kamen Rider series embodied -- When they died, they got magic resurrection buttons. Well, one of them had to wait forty years, but still.

I'm currently in the middle of re-watching Wizard after having not seen it for a few months, so this explanation could definitely stand to be a lot better. But there you have it!

Magical girls of all types are actually my main fandom and I love older style ones too. Koyomi sounds very interesting. I didn't read your spoilers, but I might have to actually watch a Kamen Rider series. You also make Haruto almost sound like a Precure with the way you describe him.

So, tell me about Mayu.

I haven't seen Precure but I just relayed that comment to my roommate, who has, and he said that's about accurate.

So, Mayu! After her twin sister became a Phantom (one of the series' despair monsters) Mayu did her best to carry on. That Phantom later came after her, aiming to drive her to despair as well and create another Phantom, and despite Haruto's attempts to protect her she still wound up on the brink of despair. She overcame it on her own, though -- the first person in the series besides Haruto to do so -- and earned the right to become a Kamen Rider on her own.

After vanishing for a few episodes to practice her magic, she showed up to try and take her revenge on the Phantom who used to be her sister. She's highly driven and incredibly strong for a high school student. Plus she's the first female Kamen Rider to appear in-series (as opposed to just in a movie) and have a significant role without dying for it, and she's definitely not a disappointment.

Ketsu covered the telling about, so I will serve simply to drive by and drop some shiny transformation gifs on you of Mayu.