MyLittleBrother
If you use the excuse that you don't remember or don't know what happened in 3 months, then you could also use the excuse that someone in those 3 months made him make magic. Probably he will learn sword skills by hiding his magic power, then he will become mage swordsman. I don't like I don't like power-hiding events.
The previous Leo was probably a harem protagonist. No magic. Strongest knight at school. Killed a lot of vampires. And from the previous chapters, it looked like he had a pretty âgoodâ relationship with the female characters introduced. The only problem was that his Plotarmor wasnât strong enough during a critical moment and died(I am guessing) and one of the love intrest/s used a technique or ritual to bring him back but ended up bringing a Leo from another world. They could have also been trying to bring a similar Leo to theirs from a parallel world but they just werenât lucky enough.