Masamune who won a great amount of cardgame tournaments before has to defeat the demon lord in another world with nothing but the help of his trash cards and the guidance of the goddess Mieri. However as it turns out, the skills of all his party members were also pretty useless.... (Source: Kadokawa Books, translated)

I began living by myself ever since I entered high school, and all of a sudden, my teacher Ms. Mitsuki proposed to me. Her hairstyle and clothing are different, but could it be that… she’s the woman living next door who I have a crush on!? But, how can we marry with this age gap! Even so, we began to date (tentatively)… “Pass me your keys. I’ll go make a duplicate.” “Huh!” Whether day or night, she barges in my apartment from next door, and flirts with me relentlessly in school whenever there’s a chance to! The girls in my class even almost found out about it—Ms. Mitsuki, are you serious about marrying me!? The love comedy of a beautiful and older teacher who lives next door and her student begins! (Source: Overlap, translated)

A school girl named Eri is magically summoned by a magician named Rex, intent on doing some scientific research observing people from different worlds. Instead of being terrified about her current situation, Eri manages to secure Rex’s promise to summon her again every week. After all, being in a magical world is a lot more exciting than life as a school girl. (Source: MU)

The Ten'hearses Academy is a school for students who have acquired a "Secondary Name", an ability that can be activated by borrowing the power of heroes. Ryoma, who doesn't have this ability, goes on a labyrinth expedition with his party, and sees a silver-haired girl named Hilda bathing in a jungle spring. Hilda, who saved the party in the underground labyrinth, appears at the school and suddenly kisses Ryoma. This is a supernatural x adventure fantasy that unfolds in the mysterious labyrinth of the school! (Source: Ichijinsha, translated)

Otoboke Kachou is another 4-koma offering from Ueda Masashi-sensei. It began serialization in Manga Time in 1981 and continues till this day. The series follows the comical trials and tribs of the titular, yet simultaneously pompous and klutzy section chief Otoboke.