The Glory After Rebirth - Chapter 489 - An Offensive from the Wan Kingdom's Army

Xia Yan passed through to the world of Bleach and became an eleven-year-old boy. He was rescued by Renji and Rukia in the Seireitei, and he was studying at Shin’ō Academy, and he was a student of the same class.
He is a top student of the Shin’ō Academy, and he is vying for strength by various teams. In the end, he has entered the first team of secret mobile maneuvers.
He will use punishment to kill every person who tries to threaten the martyrdom and protect his loved one.

- Description from Novelupdates

He became a teacher at the best magic academy in the empire.
….For being mistaken for someone else.

In the nation of Avrael, power is both a blessing and a curse. Sixteen-year-old Ayato Daath, a poor orphan, had always hoped to live unnoticed in the shadows of the city. But when he is forced to undergo The Rite of Manifestation, the ritual that determines one’s magical potential, his worst fear comes true—he is an Elite.Now torn from the only life he’s ever known, Ayato is thrust into a brutal world of magic, bloodshed, and treacherous politics. In a society where the strong prey on the weak, where rival factions scheme in the dark, and where a single misstep could mean death, Ayato must quickly learn one thing—adapt, or perish. And one thing Ayato already knows is that in Avrael, only the ruthless survive.

A fluffy, sweet modern GL story about a mature older women and a cute university student.