There's not supposed to be any air in the bladder though... Or am I mistaken?
There's no air in the bladder, correct. It stretches like a balloon upon filling and returns to a lesser stretch upon emptying
Sawa-chan's kidneys are stimulatedUreterUreterUrinary bladderA large amount of urine flowing into the bladderAs urine gathers inside the bladder, the wall muscles expand and a signal is sent to the brain, causing the urge to urinate.UrineBlood is filtered and urine is formedRenal pelvisMinor calyx※Not making physical contact (important!)To urinary bladderSend mystic energy into Sawa Azusa-chanBack, around waist-levelUreter opening (left)Bowman capsule fever!!Urinary bladder wallInternal urethral openingThe urine made in the kidney is transported along the calyx → renal pelvis → ureter to the urinary bladder.(Rear view of Sawa-chan's kidneys)Here