#4966

What anime is this?! I've already found the song.

I found a video what possibly is the source of the loop:
"Crossfade - Under ! Where ?"
YouTube-Link

This video is an AVM (Anime Music Video) and is made of a variety of animes. Here's a list of all animes used in this video:

Amagami SS
B Gata H Kei (TV)
Baka and Test - Summon the Beasts (TV)
Bakemonogatari (TV)
Demon King Daimao (TV)
Denpa Onna to Seishun Otoko (TV)
Detroit Metal City (OAV)
Heaven's Lost Property (TV)
Heaven's Lost Property Forte (TV)
K-ON! (TV)
Ladies versus Butlers! (TV)
MM! (TV)
Motto To Love-Ru -Trouble- (TV)
Omamori Himari (TV)
Oniichan no Koto Nanka Zenzen Suki Janain Dakara ne!! (TV)
Princess Lover! (TV)
We, Without Wings (TV)

(Source)

I hope I could help you
~SunRed

Thank you for your help ^^