Gate: Jieitai Kanochi nite, Kaku Tatakaeri, Kono Subarashii Sekai ni Shukufuku wo! Recommendations
I'm surprised no one has recommended it yet. Both anime are about an Otaku MC who takes a mission in an alternate fantasy world. The heroines from both shows also look alike: a Goddess, a loli mage/wizard, and a blonde who's the tallest girl in the group. Both are action packed anime with comedy. The difference is GATE is about military while KonoSuba is purely an adventure in fantasy world.
Ever wondered what it would be like in a different world? Itami and Kazuma can tell you themselves! Both MCs are otakus who have to finish their mission in a different world. Both of them also have 3 female companions with different personalities that help/go along with them on their quest. Action, Fun, and Laughter: the 3 words that perfectly describe the 2 series.
These two anime share the same lighthearted atmosphere and have very similar settings. If you enjoyed the fantasy theme and comedic elements in Gate, you'll probably enjoy watching Kono Subarashii Sekai as well!
There are 2 seasons. Both are funny. Both MC are transported to another world to fight mythical creatures. Action scenes are good and has funny moments.
Both are comedies with fantasy worlds. Gate is a bit more serious and Konosuba has more fanservice.