I have a game called "Dr Kawashima's Brain Training How Old Is Your Brain?" and I want to speedrun it but I can't find a leaderboard for it. Can someone help me as I don't know what to do.

If you want to speedrun a game that is not on speedrun.com, you can request the game here: https://www.speedrun.com/requestgame?series= Keep in mind that you will automatically become a moderator of the game which means You'll be responsible for verifying runs, creating leaderboards etc.

A bit late to this but Brain Training is called "Brain Age" on sr.c because that's the name of the US release Heres the link to the page https://www.speedrun.com/brain_age