This isn't very good.
I'm really not a big fan of the whole "reincarnator wakes up in a teenage body and goes to the hunter academy" setting, and the story doesn't do a whole lot to justify the setting either. The MC just kind of ends up in the academy for no real reason, and then stumbles upon a pretty arbitrary reason to stay that involves advancing the plot in a pointless direction.
He finds out that one of his old followers who might be able to help him has a daughter that goes to the academy and also she's the student council president and a pseudo celebrity.
So he thinks "I'll join the student council and become friends and then ask her to introduce me to her father.", which is just really contrived and definitely doesn't sound like it would work.
The story doesn't really do a good job explaining power rankings or power levels beyond the usual S, A, B, C, D, E, ratings, but I suspect they only exist here because like the academy setting, they're in every other novel and the writer can't be expected to be original, I guess.
The MC is leagues more powerful than any of the students or even the teachers in the academy, and can basically play with them during battle without issue, but at the same time, the power levels in this story seem to be based mostly around equipment?
The weapons in this world seem to be very important because they allow hunters to use skills, the MC borrows a ring relic from his old friend, and he's able to unleash skills using it, so does that mean without a weapon he can't use any of his skills, who knows?
The MC has no idea when the Big Bad will actually reappear, the only timeline he's aware of is 47 years later, but when he woke up it was already 47 years later. So for all he knows the Big Bad could pop up literally tomorrow and humanity would be completely destroyed again.
Instead of just using his power to force his way through the stupid restrictions he's being met with, he decides to cosplay as a student and go on field trips and try to build relationships and use that to move forward with his flimsy plan.