Shikiyoku Musou: Hentai Skill ga Bousou Shite Yarisaa kara Tsuihou Sareta Ore wa, Hakarazumo Inbi na Chikara de Saikyou ni Naru

Rick, a member of the "Yarisa" (Spear Club), an adventurer group for spear users, awakens to a perverse skill called "Lust," which increases his combat abilities when he engages in erotic activities. As a result of becoming the only one who becomes incredibly popular, the club is on the verge of collapse, and Rick is expelled by the leader! Rick's solo adventure life begins...!?

(Source: Kodansha, translated)