Here is a list of websites that I usually go to in order to download .pdf files of music sheets for anime songs (themes and soundtracks). Some of these websites also offer sheet music for video games. Sites are written in no specific order.
note: I only play the piano and violin. That is why, some of these sites are specifically for violin and/or piano. If you play other instruments such as guitar, cello, flute, etc., these websites also offer links to other wonderful sites to get music sheets for other instruments and guitar tabs.Violin only • Free Download • Accepts Requests
Various individual instruments and orchestra • Free download • Accepts Requests
Various individual and group instruments • Free download • Accepts Requests
Various individual and group instruments and orchestra • Free download • Accepts Requests for a fee
Violin and other string instruments • Free download
(I'm not quite sure if Anime on Strings~ accepts requests! xD)
To all those musically-talented anime fans out there, I hope you enjoy playing your favorite anime, video games, and j-pop songs! :D