Bouken-sha o Kubi ni Nattanode, Renkinjutsu-shi to Shite Denaoshimasu!: Henkyou Kaitaku? Yoshi, Ore ni Makase Toke!

Craft is an adventurer with the magician's crest. However, he has absolutely no talent as a magician! One day, after having been fired from yet another party due to his lack of latent, he had his crest changed at the recommendation of a crest inspector. His new crest turned out to be the legendary "Twilight Alchemist"! Craft, the weakest magi turned strongest alchemist, now sets out to slay monsters! ...Or not! Instead, he'll be settling the frontier! Unaware of his potential, the legendary alchemist's peaceful life starts here!

(Source: Manga UP!)