She arrives at the place where the letter invited her, and everything suddenly goes black. When the lights return, she notices that the sky has become purple, and her magical guardian isn't present. Another magical girl arrives and informs the protagonist that this is a space only magical girls could enter. The mysterious girl then starts to cast a spell, and regardless of what the player does, she succeeds at casting it. The player gets a game over screen, but don't be fooled: you just have to start the game again.
Everything starts with the protagonist having a conversation with her magical guardian yet again... until she starts to feel like they already had this exact conversation before.
a letter of challenge provides examples of:
- Color-Coded Characters: The protagonist has pink hair and clothes, and the mysterious girl has blue hair and clothes. The protagonist's guardian is completely yellow.
- Defeat Means Friendship: The mysterious girl eventually admits that the whole reason she sent a letter of challenge and set up a battlefield for her and the protagonist, rather than just clearly state her true intentions, is because her only other friend is an ex-villain who tried taking over her town before they fought and became friends.
- Determinator: The main protagonist willingly and repeatedly subjects herself to the mysterious girl's time rewinding magic, without any knowledge of how to stop it, simply because she believes it's her duty to deal with it.
- Digging Yourself Deeper: When the protagonist and the mysterious girl finally get to have a full conversation, the mysterious girl admits that this is the first time someone else has noticed her time rewind, and the protagonist is concerned that the girl tries to solve all of her problems with a time rewind. The girl then suggests rewinding time in order to never send her the letter and try to prevent the time loop mess from happening in the first place, and the protagonist says that's exactly what she doesn't want her to do.
- Evolving Title Screen: When first starting the game, the full title is displayed, the background is a dark navy color, and there's a picture of an unopened envelope with the titular letter. After reaching the ending, it changes so the envelope is now open, the background is a much lighter shade of blue, and the full title changes to a letter of challenge (& friendship?).
- Fission Mailed: After the mysterious girl casts her spell, the player gets a game over screen. However, starting again will continue the story, as there is a time loop.
- Forgotten First Meeting: In the end, it turns out that the protagonist and the rival magical girl have indeed met before. Two weeks ago, there was a huge battle between a bunch of magical girls and a giant monster at a pier, and the protagonist saved the other girl from being knocked off. The battle was so intense that the protagonist doesn't remember all the details, but the other girl thought she was really cool and wanted to befriend her.
- "Groundhog Day" Loop: Every time the mysterious girl casts her spell, time resets back to when the protagonist was returning from school, right before she found the letter.
- Instant Costume Change: Whenever the protagonist is warped into the mysterious girl's battlefield, her school clothes instantly shift into her Magical Girl outfit. Her clothes also instantly swap back when the other girl finally dispels the battlefield, though the other girl keeps her own magical girl outfit on because she likes how it looks.
- Leaning on the Fourth Wall: If you repeatedly perform an action that failed in one of the previous time loops, the protagonist will question why she keeps doing something so useless and say that it's almost as if someone is forcing her.
- Luminescent Blush: Towards the end, as the other girl recalls the time the protagonist saved her during a monster battle, she gets a notable blush while describing the protagonist's actions as "really cool", and again when she asks for the protagonist's phone number to message her later.
- Magical Girl: Both the protagonist and the mysterious girl, who are ordinary schoolgirls with magical powers that are stated to be meant for fighting against villains.
- Minimalist Cast: Besides the protagonist, her magical guardian, and her rival magical girl, no character ever appears onscreen.
- Nameless Narrative: No character in the story has a name. The game's antagonist is usually referred to as "the mysterious girl."
- No Social Skills: The mysterious girl; she eventually admits that the only letters she's ever received were letters of challenge, and her only other friend is an ex-villain she had to beat up first, which is why she misguidedly attempted to befriend the protagonist in a similar manner before getting anxious and trying to undo the whole meeting. She's also never had to save a number in her phone before and has to be taught how.
- Officially Shortened Title: The game's opening screen depicts the full title as a letter of challenge (& magic!), but the part in brackets is dropped on the download page. Mainly because it changes after reaching the ending.
- Poor Communication Kills: The mysterious girl wants to befriend the protagonist, so she summons her with a letter and creates a barrier only magical girls could enter to talk to her. The protagonist ends up thinking that the mysterious girl wants to fight her. The mysterious girl, instead of simply explaining her intentions, turns back time, as she feels like she has messed up her only chance to talk to the protagonist. Had the mysterious girl simply explained that she wanted to be friends instead of turning back time, the entire conflict could've been avoided.
- Puzzle Boss: It's impossible to defeat the mysterious girl by fighting her, as the player doesn't have enough turns before she casts her spell and resets time. Rather, she is defeated by the player doing nothing for a certain amount of time, resulting in them skipping a turn. However, this doesn't become an option until the last time loop.
- Ripple-Effect-Proof Memory: The protagonist remembers every iteration of the "Groundhog Day" Loop she undergoes, unlike her guardian. The mysterious girl also remembers, but doesn't believe that the protagonist really does, which is why she keeps wanting to make the best possible "first" impression.
- Sheathe Your Sword: After attempts to battle, run from, and talk with the mysterious girl all fail, the protagonist's guardian suggests thinking outside of the box, and simply doing nothing in order to convince the girl that the protagonist doesn't consider her a threat.
- Stating the Simple Solution:
- Upon first learning about the time loops resetting the protagonist to before her encounter with the mysterious girl, her guardian asks why she can't simply stop accepting the challenge. The protagonist simply replies that anyone making magical barriers without permission needs to be dealt with, and it's her duty as a magical girl to try, even if she isn't yet sure how.
- In the end, the protagonist has to repeatedly make clear to the mysterious girl, who set up an entire magical arena and repeatedly cast a time looping spell in order to befriend the protagonist, that the simple solution is just having a conversation. It takes a while because the other girl has never made a friend without fighting them first.
- Title Drop: The titular letter of challenge is what the protagonist finds in her gym bag at the start of the story, which leads to her first encounter with the mysterious girl.
- Waiting Puzzle: In the last time loop, the player doing nothing for a certain amount of time results in them skipping a turn. Doing it multiple times will lead to the mysterious girl finally talking and explaining her motivations, as she now understands that the protagonist doesn't want to fight.
- Wake Up, Go to School, Save the World: The protagonist is a regular schoolgirl when she isn't acting as a magical school, and the first few loops start with her mentor joking about her clumsiness in gym class, like missing the birdie in a game of badminton and having it hit her head instead.