Isekai Ojisan

Coma héroïque dans un autre monde / Isekai Uncle / Ojisan in Another World

Having survived an isekai for 17 years, 34 year old Ojisan (uncle) returns to modern day Japan. Takafumi, Ojisan's nephew, now gets to witness what throwing a diehard Sega fan into an isekai for 17 years does to various things and people, both past and present.