Chapter 88- Fifth Layer (Part 1)
Akio was then led to the stairs that lead up to the higher floors. He didn't even need to go back to the cell he was in since he didn't have any baggage or any attachment to it even though it was his room for the past few weeks.
The only thing he had belonging to him was his Blood Eye Odachi, the sword that he still yet to use since he didn't find an opponent worthy enough for him to reveal his trump card. So, he kept it hidden.
One of the functions of artifacts that get dropped from enemies is that the user can simply make them disappear and reappear on command. Seraphine explained that this is one of the 'Inner World' functionalities that no one from the Lower Realm knew about.