World's End Harem: Fantasia Vol. 6 (manga)

The knight Celine has returned home to Nargala at last. With her help and that of the sorceress Joanna, Arc manages to stall the progression of his father’s illness. But before he can put further plans in motion, a voluptuous high elf named Felaris comes to him with a request. Her hometown is under attack, and in exchange for Arc’s assistance, she promises all kinds of rewards—both magical and more earthly delights.