Possibly the Greatest Alchemist of All Time

Takumi Iruma, a salaryman going on 40, is summoned to another world by accident; unable to return him to his world, the Goddess Nolyn asks him to try living as a 17-year-old boy in her fantasy world of Mildgard; Takumi is set loose on the world.

Maple, the spider monster that Takumi meets in the forest and tames, possesses the skill to create Spider Silk; the silk becomes a hit amongst the villagers.

In order to create 100 of the toilets equipped with a magic device that Papek begged him for, Takumi visits the Mulan Company to procure help.

Takumi informs Maria and Sofia that he'd like to travel, so he registers them both with the Adventurer's Guild and forms an official party.

Takumi wants to upgrade their gear for their journey, so he seeks out mythril and admantite ores; after consulting with the Adventurer's Guild, he accepts Quests to defeat monsters, gather Treant Wood and escort a miner to excavate the ores.

Word of Takumi's Purification magic device reaches the Holy Empire of Sidonia; they demand that the Kingdom of Barcula hand over Takumi, but they refuse.