Ano Toki Tasukete Itadaita Monster Musume desu. Full Chapters                    

Ano Toki Tasukete Itadaita Monster Musume desu. is a Manga/Manhwa/Manhua in english language, Ecchi series, english chapters have been translated and you can read them here.

Some 20 years have passed since the protagonist was summoned to another world and retired from the army. He is still single in his 40s and lives as a low-ranking professor, until one day, an elite ‘monster girl’ transfers into his class.