Isekai ni Shoukan Sareta nda kedo, Nandemo Kireteshimau Kennou o Te ni Ireta no de Easy Mode deshita.

One day during school, Haruki Ito is suddenly summoned to another world along with his teacher and all the students in his class. In this new world, the boys and girls were paired off, locked in a prison cell, and drugged into physical relations with each other. Haruki is paired with Shizuka Inoue, a girl who dresses plainly in school, but who turns out to be a beautiful girl. The men are eventually released from the prison, but the women remain held as hostages, to force the men to fight monsters for the good of the kingdom. Haruki, who was only reluctantly training and fighting monsters to help Shizuka, one day realized, "I'm...... quite strong, aren't I?" That was when he finally awakens his real power.

(Source: Orgis Novel, translated)