The duet unit between utaites Soraru and Mafumafu, also known as Sorairo Muffler. Sorairo Muffler teamed up in 2014 with the cover of "Umiyuri Kaitei Tan" Nv and quickly became the most popular duet unit at present. Their covers are always in Top 4 of Weekly Niconico Utattemita Ranking and got their first No.1 with their cover of "Chuubyou Gekihatsu Boy" Nv. They also have 2 covers reached over 1 million views which are "Umiyuri Kaitei Tan" and "Chuubyou Gekihatsu Boy".