If I remember correctly Riddle's Tsum was a bit of a troublemaker and I can only imagine it just shamelessly wanting to be babied by you, side eyes it's counterpart like 'you could have this too if you weren't Soo prideful.'

If any tsum deserves to give you the railing of your life, it’s Ridotsum. AAAAAA OTL such a troublemaker but still so precious. The only tsum out of all of them who doesn’t act exactly like its human counterpart. Shamelessly allowing itself to be babied and loved by you, to be cradled in your arms and rocked to sleep. Being so close to your chest…….. oh, the things cute privilege will get you. >_<

Riddle’s had to drag the tsum out of your arms on many occasions because it keeps snuggling into your chest. >:O how indecent! Does the tsum have no regard for personal space?! You assure Riddle that it’s okay. You’re sure the tsum just enjoys being held and tossed up and down, which is true, but then you miss the way the tsum looks directly at Riddle while you’re busy fawning over it. It must be tough to be confined to one’s own dignity so much that one can’t even put it aside to enjoy a little love from you. :) it’s okay. The tsum will soak up every ounce of affection you have to give in place of Riddle. Riddle can live vicariously through his tsum.

Or: the tsum is the reason Riddle finally snaps and (softly or roughly) non-cons you. <3