2007core is a genre of webcore originated from the mid-2000s that reached its peak, as said, around 2005-2007 and began its loss of populatity in 2010's. Its main themes are the japanese and anime culture, as well as the first forums and memes that emerged at the time and the emo / scene aesthetic.
Aspects and different sides
We can distinguish three main aspects of this subculture; the first is the most Visual Kei and lolita -ish side, with the music, extravagant clothing, and the gothic vibe radiating from everywhere, especially in animes such as Vampire Knight, Death Note or Black Butler, huge successes back then. These animes also hugely influenced the 2007 culture. Recurring elements in this side are gothic architecture and clothing, as well as chains, roses, daggers, chessboards (yes many chessboards), and in artworks, a very singular and detailed artstyle.
The second main side of this aesthetic is the most "kawaii" one but also the most vague do define. This side is made of the low quality, first real "weeb" videos and images we can find on youtube after many hours of research. This contains the first beginnings and all the videos of the Vocaloid culture, with signature clips and music videos found on nico nico douga, the japanese youtube. If the video is in good quality though, the aesthetic will be extremely harder to show. Recurring elements are much closer to the Webcore aesthetic's ones, such as stamps, vocaloid songs, sparkly kitsch edits made on blingee, and low quality amateur anime-ish music videos.