[Sunder the Gold]

Spoilers for end of the anime:

Spoiler for Noumi:

I think Noumi's just pretending to be so innocently nice, now that his memory is gone.

Dusk Taker was born from mental trauma that pre-existed his career as a Burst Linker. It's not like losing Brain Burst would suddenly wipe away Haru's self-esteem issues or desire to fly away from his troubles, so losing Brain Burst wouldn't suddenly cure the emptiness that Noumi felt and tried to fill with stealing.

Besides which, if Noumi's brother was such an asshole to him once he became a Burst Linker, it stands to reason that he was an asshole to his brother BEFORE he made him a Burst Linker. Because of his brother always stealing from him, and needing to steal to meet his brother's demands, Noumi became an empty thief in real life. That's why his avatar was Dusk Taker.


So why is Noumi acting nice and cheerful despite still being a twisted wretch inside? Because without his memories of Brain Burst, he doesn't see anything to gain from targeting Arita Haruyuki, and he doesn't remember the blackmail he had.