Serum

A supersoldier from future earth, after a mission gone wrong, is betrayed and hunted by the people he once fought for. However, through a freak twist of events involving a stolen classified portal and some odd serums, he ends up getting dragged along by a psychopathic criminal through this portal, never to be seen again.

Until he woke up to the sound of... crying?

A super-soldier is reincarnated as a child in another world, one full of new people, places, and opportunities. This time, he's dead set on living it in a brighter, happier way, thinking he's finally gotten a life away and safe from the Earth and its dark, manipulative hands. However unfortunately, destiny has other plans in store...