Mannen D-Rank no Chuunen Boukensha, Yotta Ikioi de Densetsu no Ken wo Hikkonuku

One day, a forever D-rank middle-aged adventurer, Lucas, pulled out the legendary Holy Sword in a drunken stupor and became the strongest! Ever since that day, Lucas’ fate was greatly changed forever. Seeking love and to sate his desires, the reborn middle-aged adventurer's real adventure starts now!

(Source: MANGA UP!)