From the Start, I Become a Hostage in an Enemy Kingdom

Jiang Liuyun, a world-famous assassin, dies suddenly while grinding away at a game and transmigrates to another world, where he becomes the empire's Seventh Prince.

But from the start, he is sent to the enemy nation as a hostage. Luckily, the System arrives and helps him slaughter his enemies. Anyone who dares stand in my way, I'll kill!