First, be aware that your working title is rather similar to
Children of Mana, which was a DS game from 2006. You may benefit by using a different title.
Second, you said you've created sketches of your characters. Please state if this is a work in progress -- in other words, something that you're currently writing and coding.
Wirelessheart wrote:
A young girl named Mizuki who was a shy yet cheerful lost her parents at the age of seven. When Mizuki was seven she saw her parents being killed by a man she didn’t know. But before they died fully her parents told her that they werent her real parents. So they gave her a music box who was originaly from her real mother and that the music box will one day explain everything.
It sounds like Mizuki is given an
orphan's plot trinket. This concept has existed for decades, or maybe hundreds of years. It can be done well, but it can also be a cheap way to patch plot holes and solve problems.
Wirelessheart wrote:
But while the time pass she meets some boys and a girl who is the most popular students on school. And by time Mizuki start to socialize with them, will she ending up being their friends and mabye get a lover?
Genre: Comedy, Drama, Action, Romance, Fantasy
It sounds like your story will have some school-centered slice of life, but it also sounds like there will be a larger plot. How much emphasis will be on day-to-day events, and how much emphasis will be on the general plot? Balancing the two is never easy...
Likewise, I'm not sure if you plan to include romance options. Your characters can certainly be friends or significant others without the story focusing on romance, or turning into a love triangle / harem story. It's your decision.
Aside from that... it sounds like Mizuki has some type of magical or supernatural powers. (If I'm wrong, correct me.) How many other people in your fictional world will have similar abilities? Are they being persecuted or hunted down? Can a person hide their powers for any length of time? Can these people use their talents in a company or an organization?
Where does your story happen, and does it occur during a specific year or era?
Finally, if you have any trouble with Renpy, or if you need help with writing, be sure to ask. Hopefully your project will go well.