I think they are genuine. So far Arhad is the only one with the memories of the devil during the God’s Era. Everyone else with a devil fragment seems to have the obsession of Ianna in the parameters of their personal obsessions. The obsession of Roberstein inside the devil is proof of how deeply he was attracted to her. It went so deep, it’s in each of the fragments, the core pieces of the devil.
No, Arhad IS in love with in Ianna. From what I've seen, it used to be a usual form of obsession for Ianna, as if she belonged to him (as an item he must have), which made me hate Arhad for quite a while, but now, I feel like Arhad have truly fall in love with Ianna and his overprotectiveness is that of a lover instead of an item ╮( ̄▽ ̄)╭
*SPOILER*
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So because of the devil's deep love and obsession for the god Roberstein, those who possess the devil's fragment feel the same for her as well. Well, the era of gods has already ended but we all know Ianna is the reincarnation of Roberstein. Their emotions towards Roberstein is directed towards Ianna. This is why this insect is so obsessed with Ianna. This goes for all those who possess the devil's fragment. Which means Arhad's halfsiblings and their mother. Which is even more interesting because Arhad's half-brother has memories of the last timeline.