watch adult movies that randomly show up at the cinema till you find ones that are affective for dom's things like "punish me" "does that(or this) feel good" etc. ( havent unlocked them all) and continue with foreplay untill shuu decides he doesnt want to wait anymore or skip foreplay and select "become sub bottom" both you would need to do a few weeks for it to take effect (btw i havent done this myself but it should work if anyone has better ideas or ways let us know)