Brain Age (universe)
The Brain Age universe (脳を鍛える, Brain Training) is a series of educational puzzle games for the Nintendo DS, 3DS, and Switch, first released as Brain Age: Train Your Brain in Minutes a Day! in 2005. It stars real-world neuroscientist Dr. Kawashima who teaches different exercises for training and maintaining one's brain (or improving one's "Brain Age", as the series is named for).
The following characters from the series are spirits.