The concept of Gensokyo billiards is very unique! The theme-fitting portraits are really cool, including the outfits and talking animations.
The writing sets the premise well enough. (The boulder mishap was a good comical effect, for one.) Unfortunately, the genAI involvement detracts from the experience for me as it tends to add a dry feeling, for lack of better words. I encourage you to try other options for script writing & checking!
If it helps, I have seen a few different writing approaches around. For example, the scope might get limited to quick dialogues in order to write them thoughtfully. Many devs ask around to get good advice or insights, even if they're not able (or looking) to outright recruit a writer. Sometimes, a dev will even approach with visual storytelling, conveying the story via images rather than words.
(Examples from this jam include 「 Tewi jumps off a Mountain and Dies GAIDEN 」 (to an extent), 「 Finding Alice Margatroid III」, and 「 Seiga Draws Ofudas 」.)
As for the gameplay, I enjoyed seeing the random ball formations (ex: carrot, yin-yang symbol), which - combined with the character abilities and hole multipliers - made for some fun variety. On the other hand, the game turns ran extremely slowly. If the balls were to slow down faster at low speeds, the turn-end detection might run faster and help with the flow.
The game does fare well with its visual presentation front and center, though. Well done there!