Am I Really Invincible?

The protagonist is king in reality. But he was hunted down. The protagonist began to realize whether the world was right or wrong. He was obviously a party to uphold justice but ended up like this. Finally died. But arrived in another world. He was born invincible in this world. A king's master taught him invincible swordsmanship. Later, he entered the world, and later became invincible in this world. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.