Looking at the Pixiv tags to try to see some context (like maybe it's a reference to a specific game besides Touhou), I saw a tag that said "The seventh day of every month is Rumia Day", but nothing that explains why a Western Medieval Knight is entertaining a youkai in a ruined house with gravity-defying wall segments.
Looking at the Pixiv tags to try to see some context (like maybe it's a reference to a specific game besides Touhou), I saw a tag that said "The seventh day of every month is Rumia Day", but nothing that explains why a Western Medieval Knight is entertaining a youkai in a ruined house with gravity-defying wall segments.
"The seventh day of every month is Rumia Day" is just a monthly thing for some artists. Like the influx of character pictures on their birthdays, except Rumia has such a day once a month.