Once he entered the 50th floor, the black mass transformed into an exact copy of Kang Oh, Blood and all.

After confirming that it was wielding Blood, he immediately switched to Demon Sword Ubist. The Doppelganger was unable to copy Kang Oh's swap.

'The information was right.'

Kang Oh, who hadn't gotten much out of Bart, had looked through several sources and found a few tips.

The Doppelganger's copy ability had a cooldown of 2 minutes! In other words, it wouldn't be able to switch to Ubist for 2 minutes! Plus, it copied the target's HP too. Unlike most bosses, it didn't start with a ton of HP.

Thus...

'I'm finishing this in 2 minutes.'

That was the method Kang Oh had chosen.

He could use Devil Trigger or Gluttony to instantly multiply his strength several fold. But what if his opponent didn't have much HP to begin with? He could use them to completely overpower his opponent for 2 minutes!

Kang Oh used Devil Trigger.

He instantly transformed into the Jet-Black Demon, and then pulled out an item he'd prepared to use against the Doppelganger. It was a scimitar that shined silver. 

Crescent Moon Shaped Scimitar!

It was an AA-rank...