The Boy I Saved Becomes the Mech King - Episode 4

Young Rex sells lemonade with his battered mech Wisp until the Mech King Victor saves him from bug-beasts, gifting a core and warrior badge. Years later, wealthy Rex rescues bankrupt, betrayed Victor from his traitorous heirs and rival Samuel, who's corrupted Volt with alien tech. Together they destroy it and reunite to fight the bugs