Re:leaf - Re:member
Vocal/Guitar: 岡本照範 (Terunori Okamoto)
Vocal/Guitar: 土屋博幹 (Hiroki Tsuchiya)
Vocal/Keyboard: 飯田泰恵子 (Taeko Iida)
Drums: 高松延三子 (Emiko Takamatsu)
/u/Escrypthia on reddit posted this song to /r/JapaneseMusic and asked to know more about this song and the band. It doesn't say much on the video, and despite the video having more than 100.000 views, there wasn't much information to find. The band members' names are in the description of the video and the channel has a video of Re:leaf's cover of Maroon 5's Sunday Morning. The keyboardist, Taeko, also has a Youtube Channel, with a few other Re:leaf videos.
Other than that, it seems certain that this is the final song the band did, written to commemorate their time together.
I also really liked the song, so I wanted to gather all I could find about the band here, including a translation of this song.
My good friend helped me transcribe the lyrics of the song ♪(๑ᴖ◡ᴖ๑)♪ 美帆、いつもありがとう～
The picture is from this video from Taeko's channel