The gif and mus files come in .zip format. Most modern OSes will open this without a problem, but you might need an unzipping program of some kind such as WinZip. The pdf files can be viewed using Adobe Acrobat Reader.
To view, transpose and print MUS files (inside the .zip files), download Finale Notepad for free.
Oath Sign (Transcribed by HeyGways)
for Violin | pdf |
Oath Sign (Transcribed by Jin Teramachi)
for Violin, composed by Ayasa | pdf |