[Author's Foreword: This is my interpretation of the PC-98 era of the Touhou games. It's about the relationship between Mima and Marisa, as well as Shinki and Alice. There are other characters, but it is mostly focused on those four. However, keep in mind, while this is connected to my Touhou Fanfiction About Nothing series, Mentor and Protege is not a straight-up comedy either. There will be genuine moments of drama in this. Also, keep in mind, I have had the chance to play the PC-98 Touhou games on an emulator, but I didn't get very far on any of them, (and I couldn't get the emulator to work properly, anyways) so whatever I couldn't extract from canon, I filled in with my own fanon. Enjoy.]
There was a sanctuary of sorts for the humans of Gensokyo. This sanctuary was a village appropriately known as "Human Village." It was here that the humans gathered to live, and to protect themselves from the youkai. Though youkai vastly outnumber humans, the average human was stronger than the average youkai, and a whole town of humans could stave off any youkai foolish enough to enter the village, thinking it could "snack" on one of the humans.
Many humans of Gensokyo know basic magic. Not all humans, but many of them know basic danmaku attacks, in case youkai come running in. However, most humans don't strive to become incredibly gifted in magic. Then again, most humans are not like Marisa Kirisame.
Marisa was the only daughter of a husband and wife who lived as peasants in the human village. Marisa herself was considered "cute" by human standards; her hair was blonde, her eyes were a light shade of brown, and, being a child of seven, she was short and tiny. She was a student at the local school, and at school, she had learned a talent that turned her into who she is today; the talent of reading. However, books on academia did not interest her in the slightest; books on magic did. Only problem was none of the books in her school were about magic. She had to go to the village's library to get books on magic. However, the librarian wouldn't let her read any books that could teach her how to do "dangerous" magics. This did not stop her. She had developed techniques for "borrowing" books from the library and reading them in secret. Although she could not understand most of the words in the books about magic, they fascinated her like nothing else in the world. Shoot fireballs out of the palm of your hand! Fly high in the sky on your very own broomstick! Move so fast, the world around you slows down! The pictures in the book fired up her imagination. It was around this time that she had decided on what she wanted to do with her life; become a witch.
Marisa didn't know anything about actually doing magic herself. She didn't know how to levitate, didn't know how to shoot danmaku, didn't know how to create potions, didn't know how to manipulate fate. She knew that if she was going to become a witch, she'd had to start from the bottom up. Using the best of her reading skills, she had copied the ingredients for a magic potion down. Late one night, she snuck out of her bedroom and went to somewhere just outside the village. She was now in a forested area, only able to see because she had a jar with fireflies on her. She was looking for a kind of mushroom that grows just outside the village. As she looked around, a voice called out to her, "Why hello!" Marisa jumped up in fright, and let out a yelp of panic. She had been followed! She looked to see who it was. She saw what looked like an adult woman, one who was clearly visible, even in the dead of night. This woman had long green hair, and matching green eyes. She was wearing a blue cap with yellow trim and a white ribbon attached to it. She had a blue vest, one with white sleeves and a blue cape attached to it, as well as a blue collar. She also was wearing a long blue skirt with yellow trim on the edges.
Marisa, not wanting to be impolite, responded, "Uh, hello."
The woman, speaking in a confident manner, asked, "What are you doing so late in the night all by yourself, child?"
Marisa, still scared, managed to reply, "Um, looking for things so I can make my potion." Marisa just noticed something else about this woman; she had a translucent blue tail coming out of where her legs should have been. When she saw then, she stammered, "Look! You have no legs! You must be a ghost!"
The woman suddenly winced at the comment. She chided, "I'm not a ghost!" She looked away and added, "I just don't have any legs at the moment." and then muttered under her breath, "Not that it matters, since now I have greater mobility than ever before." She then turned to Marisa and said once again in her confidence, "So, why would you want to make a potion so much?"
When asked this, Marisa lost all fear. She smiled a wide smile and exclaimed, "I wanna be a witch!"
The woman looked quizzically at the girl, "Really? You, a witch? Dressed like that?" Marisa was wearing black pajamas and her black shoes.
Marisa stated, "Um . . . these are just my jammies. I won't have a real witch outfit until I'm ready."
The woman then said, "Well if you're gonna become a witch, you should be more presentable, like me!"
Marisa's eyes widened. Her mouth was wide open. She asked, "Huhǃ? You're a witchǃ?"
The woman responded, "What? You've never heard of me? Of course I'm a witch!"
Marisa said, "Oh. Well I've never heard of you, so I didn't know you were a witch."
The woman looked away and said to herself, "Hmm. Seems I haven't made much of an impression yet. Oh well, I guess I could tell you." She then looked at Marisa and boasted, "Then again, you were bound to hear of me sooner or later, for you see," she made a dramatic pose and shouted, "I am The Great Mima!"
Marisa smiled widely. She yelled, "Hi The Great Mima! I'm Marisa Kirisame!"
Mima corrected, "No child. It's just Mima. 'The Great' is merely a title, though a very accurate title." She then smiled and asked, "So Marisa, you wanna become a witch?"
"I could teach you lots of things, things they don't print in books."
"Reallyǃ? Like, really reallyǃ?" Marisa asked, more exuberant than ever.
"Yes I can! Why, if I were to teach you a tenth of what I know, you would become a most extraordinary witch!" Mima told the blonde child.
"Wow!" Marisa responded.
"However," Mima started, "This isn't an appropriate place to be learning magic. I won't be able to give you any lessons right now."
Marisa became distraught, "Huh? But why not? I wanna learn magic now!"
Mima commanded, "Patience, dearest. I'm formulating a plan right now."
Marisa asked, "What does formulating mean?"
Mima didn't answer. Instead, she made gestures with her hands, causing a piece of paper to materialize in front of her. She pointed her index finger at the paper, moving her finger like it was a pen. When she finished, she gave the paper to Marisa and said, "Here are instructions for when and where to meet me. Follow them if you want to learn more about witchcraft. However," Mima paused, going for dramatic effect, "There are two conditions you must follow. One, do not tell anyone about me, what you are doing, and what you learn from me. Two, do not let anyone see that slip of paper. In fact, burn it after you've memorized the instructions."
Marisa answered, "Okay!" She then asked, "How come I can't do those things you don't want me to do?"
Mima suddenly formed a wicked grin and stated, "If anyone finds out about me or you learning witchcraft, bad luck will fall upon you."
"Oh no! Bad luck! That's bad!" Marisa reassured.
Mima chuckled and added, "Indeed!" Then she concluded, "Well, I best be going now. It was nice meeting you, but I have errands to run. Bye!" And with that, she disappeared, literally.
"Bye, The Great Mima!" Marisa shouted. She then realized, "Oh no! It's dark again!" Then she glanced at her jar, "Except for these fireflies!" Realizing that trying to make a potion out of mushrooms was pointless, Marisa made her way back to her home, without anyone noticing.