It it implied in the art that the two had either retreated to a different room or the regent had ordered the others to leave as the regent is no longer on a throne and the bed materialized out of nowhere. Chinese bl artist do this frequently due to censorship in China.
like .. if you don't have special boobies ninjutsu,
don't dress like that. zero effort by the top to strip the bottom.
ugh . and he went for it right in front of everyone too