I read a manga long ago about a high school boy who gets transmigrated into another world. However it turns out his training in using the sword and battle strategies was done by his grandfather in preparation for if he got isekai'd because apparently the family has a long history of being transmigrated to that other world. Does anyone know the title or have a link?
And here I was hoping for a better comunicated side couple than the main considering author's previous works... guess I'll just go cry then ╥﹏╥