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 stimulatedThe urine generated in the kidney is transported along the calyx -> renal pelvis -> ureter and towards the urinary bladder.HereUreterUreterUrinary 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.UrineRear view of Sawa-chan's kidneysBlood 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 opening