Lmao even CN reader having the same question almost half of the Manhwa have him completely naked.
Not so much in the latest though.
Also boki2 is onomatopeic or something,
It might be something about the pushed down position/the receiving position like Wendy mentioned.
For comparison in WN the master already get ****** by now,
The Manhwa adaptation got it censored lol but they still shows some NFSW stuff lul.