You mix Sayumi's voice from the updated version with the original instrumental and you get this.
Of course a little bit of editing was required because of the different tempo and the pitch change near the end.
Sayumi MICHISHIGE was a member from the 6th generation of Morning Musume who debuted on 2003 with the single "Shabondama". After 11 years she graduated from Morning Musume, making her the longest running member (edit : she has been beaten by the Pons... -_-)
In 2013, while she was the leader of Morning Musume, a best-of album was released with "updated" older songs. Sayumi sang the updated version of "Aruiteru" which has a totally different instrumental.
