Idea:

Main concept:

Danmaku game with RPG elements, adapts to player's skill, full world-map to explore. Create your own character and unique shot type, upgrade with collectables found during gameplay.

The Garage:

Rika: Character customization and upgrades, determining shot type and options.
Rikako: Statistics and tips based on the player's experience, practice specific dodging types.
Nitori: Item synthesis system to create equipable bombs and abilities.

Character Customization:

Classes affect the initial shot type and speed of the character. Shot types can be overwritten through upgrades. Also determines base appearance.

Miko (homing shot, slow)
Witch (pierce shot, medium)
Maid (aimed shot, medium)
Beast (dual shot, fast)
Fairy (forward shot, fast)
Ghost (spread shot, slow)

Two slots for shot type upgrades, in addition to choosing shot appearance and color.
Splash damage, accelerating shots, increased piercing, increased rate of fire, etc.

Two slots for option upgrades, in addition to choosing appearance and color.
Change option formation, lock-in-place options, options do melee damange, etc.

Two slots for abilities, appear as accessories on the character.
Easy autocollect, dashing, small hitbox, etc.

Quest Givers:

Reimu: Clear new routes and collect items.
"A rumor is going around about a cave hidden behind the youkai mountain waterfall. Check it out, will you?"

Marisa: Find hidden treasures and unlock new routes.
"Mokou dropped a hint that Kaguya's got more moon treasures stashed in Eientei's basement. Could be our big break!"

Sanae: Hunt down boss/rare youkai.
"I saw that troublesome darkness youkai lurking around the forest attacking people again! Teach it a lesson, and you'll have the Moriya shrine's favor!"

Aya: Take a picture of a specific type of danmaku using Aya's camera.
"I need a nice red and orange picture for Bunbunmaru's festival issue, mind helping out?"

Alice: Fight experimental dolls and patterns.
"I planned on unveiling the Goliath model next week, but there are still some details that need sorting out. Would you like to help me collect some test data?"

Cirno: Random gameplay challenges.
"I'm so good at dodging! I betchya I can touch more bullets without getting hit than you can!"

Yukari: Phantasmal Parade storyline. Unlocked after a certain percentage of upgrades are unlocked. Rika and Nitori are kidnapped by Meira, and Rikako temporarily fulfills their roles in the Garage.

After the Phantasmal Parade storyline, more major characters start giving quests, which eventually lead to a final battle against Konngara.