in no particular order:

• big cocks (oops)
• blindfolds
• bloodplay (light)
• boys in dresses
• breathplay
• bruises
• choking
• clothed sex
• consensual rin or haru gangbang
• consensual sadism/masochism exploration
• cumplay/snowballing
• deep-throating
• dirty talk
• double penetration
• edging
• exhibitionism
• facefucking
• femdom
• hair-pulling
• immobilisation
• light/medium bondage
• multiple orgasms
• multiple partners
• orgasm denial
• overstimulation
• pegging
• powerbottoms
• rimming
• roleplay (cobs/robbers, costumes, etc)
• rough sex
• scratching
• size difference
• sloppy seconds
• sousuke getting bossed around by whoever he's fucking
• spanking
• strip-teases
• uniforms
• very consensual dubcon
• voyeurism (both parties in knowledge)
• waxplay