MERI+DIA ～マリアディアナ～

Main character is an agent of a space development company. He receives a task from his assassinated boss to attack a certain laboratory and destroy girl Theta who represents an important research. He executes this will, but only escapes with the girl instead of killing her. Organization issues a bounty for their heads, but Theta has a strong determination to follow protagonist.
Three bounty hunters set a trap, but one of them is saved by protagonist in the end, so they form an alliance. There can't be peace until new organization boss is defeated. But what secrets does Theta hide with her silence?

[From vndbreview]