Weird Rare Gun!

[REIA]

I dunno it's name I spotted it in my last gameplay. Was playing with another HUnewearl lvl 200 with me, we used nearlly all the ULTIMATE RARES in the game, that I thought i got them all but then somehow in Ult Olga fight, she pulled a REALLY weird gun! Look like a one handed mechgun, shoot like a mechgun, got the range of a rifle, sounds like a mechgun and make the damage of a gun but with the mechgun rapid fire, I was like, Ultimate weapon for a HUne to kill Olga and Dark Falz 3rd form, I dunno about the name of the item, I asked her about the name so I start looking for it but... she said the name is japanese, even with the name in japanese, got any idea where I could get it or it's name? Without it I still think my ultimate weapons collection is incomplete.