It will add Japan Alpine repositories and set Japan timezone by default.
You can customize the Time zone by setting the environment variable TZ, for example: TZ="Asia/Tokyo".
You can set a custom repository (to use instead of the japanese) by setting the variable: CUSTOM_REP, for example:
CUSTOM_REP=http://ftp.tsukuba.wide.ad.jp/Linux/alpine (do not include version or repository name, it will be added automatically).