Enough with This Slow Life! I Was Reincarnated as a High Elf and Now I'm Bored: Volume 3 by rarutori

After their time in the Dwarven Kingdom, Acer returns with his son Win to the Yosogi dojo, where the two must face the consequences of their long life spans. Win sets off on his own journey, and Acer says goodbye to the friends he has outlived. But this is not just a time of farewells; it is also a time for new encounters. After experiencing great loss and loneliness, Acer remembers the origin of the Yosogi School and decides to travel to the far east. Along the way, he meets a girl who can see spirits, a boy who uses divine arts, and even a mystic.