That Mechanic is the God of Mecha

Caleb was trained by the reclusive master Kingston. When he finally left the mountain, Kingston gave him an engagement contract for a fiancée he'd never met. In Payton City, heiress Jasmine paid Caleb to pose as her boyfriend and sabotage her arranged marriage with Johnny. After Caleb humiliated Johnny at dinner, Jasmine took him to cure her dying grandfather. The successful treatment revealed Caleb was actually her arranged fiancé. Forced into a marriage of convenience, Caleb began working at Jasmine's company while secretly using his skills to help others. His abilities were put to the test when he saved Sir Moore from a critical illness.