I saw this on Tackey & Tsubasa's official site
I'm assuming that's a special cover edition of Tackey's Sha la la / Mugen no Hane which you only can get though Tackey Shop
I'm not sure what Tackey Shop is though , it might be his fanclub ?
but it's a nice cover , waaay better than the other 3
& looks like we be getting 4 different covers for ヒカリひとつ too