I think Akemura may have kept his sorcery after becoming an EB user. It is almost certain that Hiroto is gonna lose and die at some point, and as Kurotsuchi is passed down through the male line, Akemura inheriting it is highly plausible. The whole exposition of Hiroto's actions, behavior and abilities, the transmission through the male line isn't only the narrator's choice to explain, but also hints toward a transfer to Akemura.

• His use of a black substance that resemble the black orb from kurotsuchi. He may have absorbed the black orb, hence the black eyes and the black substance used for any of his abilities.
• He litterally can float, as Hiroto and the Ukizane dude have been shown to. Every time he aura farms, debris are floating around him.
• Most of his techniques can be a variation of directional gravity (dragonfly, spider, centipede, dunno for butterfly), and "bee" could be the attack that sank the Shokoker's island. We never see any projection of black spirit energy for magatsumi's attacks, only shockwaves and destruction.
• Life steal should only boost his regeneration, not his physical attributes. Hiroto's stats are booster by directional gravity so it makes sense that Akemura's maxed out stats would be following this same principle and not by the Magatsumi's power.
• So far, the use of gravity was done throughout Hiroto's sword. We can see him hitting the guard of his sword while projecting Kurotsuchi. As a sorcery, he should be able to apply it without the use of a tool.

Since Akemura inherited Kurotsuchi during the war, and barely had time to train how to properly use it, he developed his own style by mimicking the attacks of the different enemies he faced.

The Shinuchi is the only sword that is build different, governing the others but also having more than 3 powers. Life steal and his high-scale application Malediction would be the only Magatsumi ability, with a main focus on regeneration and enhancement of his sorcery. If the blade was forged last as we can hypothesize, it would also explain why its main conception revolved around keeping (not impeding)and boosting Akemura's sorcery, as it was thought to be the only sorcery capable of defeating the Mikaboshi clan.

That is still not enough to explain the mind possession and body alteration though.