Reincarnated into a child - male protagonists

It’s a shounen ai but he goes back in time 10 years who when he was younger. To save his boyfriend from dying I guess

-goes back in time to when he’s a child
-bl
-not really fantasy but more backtracking events

The ml is born into a family that only produces swordsmen.

He learns that he has a very powerful magic ability. Kinda like a sage or something

-he’s not a child or anything but pretty young and it starts when he’s a baby sooo
-politics
-family drama
-kinda dark tbh
-revenge

Ml goes into a game/story?

He ends up being a side character who’s only ability is to blink (some fast teleportation magic)

Meanwhile he’s trying not to disturb the main story but keeps interfering with the main characters. Unintentionally changing the events.

-he’s not a child but they’re like teenagers I’ll just accept this T-T
-goes into story
-magic school
-pretty funny
-two people stuck in one story
-APPARENTLY THERES HAREM