Grimgar of Fantasy and Ash, Vol. 3 (manga)

"Eager for a new challenge, Haruhiro's party descends into the Cyrene Mines--the lair of the kobolds and the resting place of Mary's former allies. But not long after the combat starts, tensions between Ranta and Haruhiro begin to flare, and when the group finds itself up against an unspeakably powerful foe, Haruhiro is forced to make an impossible choice"--Back cover.