Possibly the Greatest Alchemist of All Time

Takumi Iruma gets dragged into a hero summoning by mistake and lands in Mildgard with blessings from a goddess who cannot send him home. He chooses life as an alchemist and blacksmith, settles near a craftsmen village, and turns practical ideas into tools the world has never seen. A rescue in the woods gives him a spider partner named Maple. In the city he contracts Maria to manage his home and the elf warrior Sofia, whose curse and sealed magic he repairs. He builds fridges and self cleaning toilets, then crafts an enchanted carriage with rooms inside. These inventions draw the eyes of Barcula’s nobles and the Holy Empire of Sidonia. Assassins come and the Divine Light Squadron makes its move. Takumi answers by warding his base, taming an Iron Golem he names Titan, and upgrading gear with mithril and adamantite mined under guard. News from Sidonia hints the three real heroes are being bent toward war. Takumi keeps working, protects his people, and proves that patient craft can change a country.