uke-kun unintentionally accommodated our sadistic seme in painting a soft core erotica situation with their verbal exchange during the hand job.
My guess is, due to the seme's facial expressions while giving the uke a hand job, uke kun has successfully awakened a new kink in seme kun since he's likely not used to such raw, erotic and unfiltered expressions during sexy times.
Poor uke kun, ganbatte! The seme's curiosity and desire for him will only intensify from here on
Sunbae, trying to manipulate a person's feelings and situations to get your desired outcomes is not only cruel but makes you seem like you lack the confidence in yourself to find love the right way.
Hopefully sunbae will learn from this and stop with his foolish games.