1. This forum appears to be using vBulletin 4, but its website style design is terrible in context of the contemporary web design aesthetics.
That style was commonly seen 10 years ago among lots of anime pirate forums in Mainland China.
I am a fan of the NewvBB-CSCN style used during vBulletin 3.0 era, and I recreated the style for XenForo 2.2:
I have my nostalgia with CS-CN (counter-strike china forum) which was popular around 2004, hence my reproduction of its forum theme for XenForo 2. This version doesn't require frameworks but I will release another version of this theme alongside...
xenforo.com
I tried my best to mix the two different aesthetic taste together in concordance.
I wonder your comment with that style.
2. It is not possible to do a 100% match using XenForo
without any degration of user experience.
XenForo is comparatively better than vB4.
3. Considering the nature of your forum (an anime pirate community)...
I am afraid that its usage might be incompatible with XenForo EULA.
(Maybe
@Brogan is more familiar with explaining EULA.)

If this problem exists, then you might want to consider free forum softwares (like
Flarum) in lieu of commercial paid forum softwares.