Tensei Mahou Shounen to Kokuin no Kenja

Ryui Atrei is a child prodigy who skipped grades to enter a magic high school at the age of 12. His true identity is that of a reincarnated person who studied magic in a previous life. In order to save his younger brother from an incurable illness, he searches for healing magic, which is considered rare in modern times. His first clue is the "Three Wise Men," great wizards with vast knowledge. Will he be able to find these legendary figures? And will he be able to protect his brother? The boy's journey begins now.

(Source: eBook Japan Plus, translated)