Board Thread:Questions and Answers/@comment-2.98.58.229-20160215175235/@comment-24726063-20160222125603

No it is different, after Guren touched Asuramaru first (LN), he developed a second personality. Asumramaru was still cursed inside the sword and Mahiru took him with her afterwards.

So I think we can assume that just the first contact with the demon weapon changed something in Gurens mind, so that he got his second demon personality. But we still shouldn't forget, that this cursed gear wasn't perfected and it seems that by the time Yu got Asuramaru it is a bit different. Because till now there was no mentioning of a second personality inside Yu. (correct me if I am wrong, but I think in the manga nobody of them mentioned a new formed personality) In the manga it looked like the demon weapon itself possesses the host and not the second personality (like Mahiru-no-yo possessing Mahiru)

So I can't give you a definite answer to this question, because in the manga the demon wants control over the body and this looks more like Yu will lose control and in turn Asuramaru will gain these control, so staying inside the body. But we have to wait, till now it also can be that Yu will form his second personality and Asuramaru will stay in the blade. (But as far as I am it looks more like his seraphim side destroys his humanity, while Asuramaru tries to safe it to get his body)

Would love to get an opinion from somebody who has a bit more knowledge from the manga and light novel.