I'm a small but thick girl with disproportionate sizes. I'm 149cm tall, have an 83cm bust, 64cm waist, but a 97cm hip. If I were to get a medium, it would fit my hips fine, but the upper half would've been loose (and I wanted to avoid the side-boob dilemma most people were experincing). I'm fine with a tighter fit, so I took a gamble and bought the small. It's a tight fit on the hips, even to the point where my thighs buldge out (because the gold part is not stretchy like the leggings), but it's nothing bothersome and can still maneuver in the cosplay comfortably since it's stretchy.
Since I have abnormally thick arms, I understood that the sleeves were going to be a super tight fit, but I followed the advice from some reviewers and cut the inside of the sleeve. Some adjustments would have to be made, like sewing snaps for the one piece to make it bathroom accessible. Overall, I feel so cute in the cosplay! Even the wig is amazing quality and I'm surprised that for a long wig, it doesn't tangle easily. Still needs styling though. Dokidoki cosplay doesn't disappoint!