Subtitle: Why noone should care here
ok so let's start this with
1. This thing is some kind of fancover on youtube accessible here and https://www.youtube.com/watch?v=oB7OTazfsSo here
as you can see it's either AmaLee & NateWantsToBattle or NateWantsToBattle and Amanda Lee by these 2 titles alone.
Then the both videos respectively say Amanda Lee & NateWantsToBattle or NateWantsToBattle + Amanda Lee or NateWantsToBattle -&- Amanda Lee (LeeandLie)

Both Videos List Kuusou Mesorogiwi as the title somehow in the titlelines
while the actual content of the Video shows either Kuusou Mesorogiwi from Future Diary or just Kuusou Mesorogiwi

hooray they clearly care about what this song is called
So since i couldn't make out which of these is more official than the other i went on to step 2:
2. How do they sell their thing?
so yeah following the links in the decription basically gives you these clusterfucks of metadata:
NateWantsToBattle feat. Amanda Lee - Kuusou Mesorogiwi (From "Future Diary")
NateWantsToBattle & Amanda Lee - Kuusou Mesorogiwi (From "Future Diary")
Amanda Lee & NateWantsToBattle - Kuusou Mesorogiwi (From "Future Diary")
.
AWESOME now I know much more than I did before the Artist writing with
NateWantsToBattle feat. Amanda Lee is on all websites where they put up the picture (which is all)

both their Facebook accounts don't give any more info on this
oh hey look on Amanda Lee's video:
http://puu.sh/ko2mq/13fced2fb6.png
look

hey guys that's a title i can use right?


this is the pic that is displayed on every place they usually sell the songgg
so I'm using the Artist writing from there which is NateWantsToBattle feat. Amanda Lee
and the title that LeeandLie's official Video suggests in the description
The title like this is also mentioned in NateWantsToBattle's upload but there it's like integrated into a sentence so ~lol~

Summuary
Artist: NateWantsToBattle feat. Amanda Lee
because that's the most common writing aound everywhere but the videos themselves
why? that's the only thing that's remotely consistent about how they write their damn artist so I'm going with the most dominant thing here
Title: Kuusou Mesorogiwi
the From Future Diary is omitted because both video descriptions do not use it in the title either and the only thing that is explicitly stated is Amanda Lee saying that this is called Kuusou Mesorogiwi

either way i don't really think any of them really cares how the damn thing is called so I'll go with this reasoning because it makes the most sense to me

ffs