I noticed that too but if you look when she spreads her lips it’s normal, then out of nowhere she uses her muscles to open it all the way for the dildo. I don’t think this is a sign of being way too loose as much as a pro that knows how to control her body
In my opinion Mika is the best asian of all time. An ass for days, beautiful all natural tits, cute face, enthusiasm for days, loved pussy and cock equally, fantastic rocking body and just a genuine love for her work.