Ultraman: The Primordial Light from the Start

[The author isn't very good at writing, so if you're not enjoying it, you can skip the first four chapters and read the Diga-focused arc. The Diga arc is pretty good.]

Lin Yu transmigrated into the Ultraman universe and was bound to an Ultraman Universe System. [Ding! Congratulations, Host, you are now the true form of Ultraman Trigger!] The System ran off less than a day after binding to him, leaving him with only a stick-shaped object. Seeing that it looked exactly like Ultraman Trigger's Spark Lens from the TV show, he went on to make a name for himself in the Ultraman universe.