Null Skill Rebellion from Another World

Students from Japan are transported to another world where ancient bloodlines once produced legendary Heroes except one isn't like the others. One is American whose ancient family migrated from Japan, Tom Muraiyama, descends from one of those families but is branded a null by the goddess and cast into a lethal void dungeon. Killing monsters unlocks unlimited skills, including Synchronize, which combines materials into new objects. He forges obsidian armor and a full-face mask, renames himself Windstar, and vows vengeance against the goddess, her followers, and the classmates who abandoned him.