301リダイレクト対応、すっかりやり方を忘れてたので。
RewriteEngine On
RewriteCond %{HTTP_HOST} ^□□□\.main\.jp
RewriteRule (.*)$ http://www.example.com/$1 [R=301,L]
あとはGAとGSCの対応して終了、かな？
A website showcasing photographs of old towns, museums, and botanical gardens around the world, captured since the 1990s.