Ultraman: The Ultimate Lifeform

The protagonist's name is Regis.

He transmigrates to the world of Tiga and becomes a Kyrieloid, a Flame Warrior of his generation. The energy released when the original body's soul crossed time and space shattered that soul, and the protagonist cannot absorb it, so he has none of the original owner's memories.

Fragments of the original owner's soul sometimes interfere with him.

He is also one of Reiblood's test subjects and possesses Reiblood's genes.

To become an Ultimate Life-Form, the protagonist begins plotting to obtain an Ultraman statue before the events of Tiga even begin.

He hopes to transcend life by fusing with the statue and become an Ultimate Life-Form.