"Answer" EP physical release has been delayed due to the volatile COVID-19 situation. Last week, Japan declared a state of emergency, including Tokyo, and prefectural government orders are shutting down non-essential businesses during this time, including CD shops.
Since CD shops are pretty much closed on the supposed release date of 22 April, it makes sense to delay the physical release of the single until no earlier than 13 May, although that is subject to change depending on what's going on with COVID-19 in Japan overall.
"Answer" song will still be available digitally on 22 April, but the cover songs will have to wait until the physical release.
https://www.jvcmusic.co.jp/-/News/A023686/641.html