Johnny, a mouse new to school with balls that grow out of control!

The school year had recently started, and the young adults in this city that attended it had all gotten alot bigger over the summer. Well, most of them had, anyway. The young, short mouse was crammed into a tram with other bigger-endowed students also traveling to the same, new school as him. Despite being the same age as the others, Johnny still stood at a full head shorter than all other guys sitting and standing around him. One other guy Johnny noticed, who had a toned physique and quite broad shoulders, was two heads taller than him!

Johnny's growth spurt had so far only boosted his muscles a tiny bit, but he didn't undergo quite as drastic a transformation as his older brothers had when they were his age and moved out. The biggest change Johnny had to come to terms with was his boosted ball sack, seemingly over productive and with a mind of its own at points, much to the young mouse's annoyance. (Good thing the school had Ejaculation Disposal Sites installed in the walls next to the bathroom stalls, as he found out during his frequent usage of them his first week there.)

A thicc and evenly-proportioned dog woman made her way through the tram to reach the other side, when suddenly the entire carriage took a sharp enough turn to make her fall over in front of Johnny. This didn't help Johnny's anxious and nervous mood, as his gaze and all other passengers gaze was suddenly focused on the yellow and white-patterned, fully exposed rear of the dog who fell down to the ground, cushioned by her bust and luckily, entirely unharmed.

The not-so-subtle wobbling of the mass of furred skin clung around a small thong and peeking out from the under the grey skirt was seemingly not eye-catching enough to make most guys and gals around give the incident a second look. But to Johnny's special balls it seemed to be enough to start swelling up. Though Jonny shut his eyes, he couldn't stop the moment from replaying in his mind. The absolutely huge ass positioned perfectly infront of him being flipped up and bouncing around like jello was just...oh--!

By now the dog had got up and simply continued her little journey, like the quick little incident hadn't happened. So, when Johnny carefully opened his scared little eyes to see if there still was a huge yellow butt laying in front of him, he instead noticed his bulging black shorts poking out, white and grey skin escaping the bottom leg holes of his shorts, and his dick head beginning to paint the front of his shorts with pre-cum. "pl-please.. not now--" Johnny prayed as he hoped they tram would let them all out soon.

A boy very visibly making his balls grow after he got a boner from seeing the dog's butt then badly hiding that he was sweating nervously seemed a bit odd to some other students around who noticed his erecting member, but who then rationalized that the short little mouse was doing it intentionally for some reason. Before being able to ponder this further, the ride had reached the school, and Johnny was first out as he sprinted to the restroom to relieve himself.

After he reached the boys section Johnny quickly went inside and picked a suitable hole for himself to let loose his many needed nuts inside. By now, his balls hung low and had swelled to round football-sized balls in his round sack. It made subtle, low-pitched churning noises inside as more semen was produced than the mouse knew how best to release. Hurriedly, but carefully, he discarded his shorts and underwear and thrust his swollen member in the rubbery, warm Disposal Site hole in the wall, his first shot firing almost immediately fast and hard into the machine as he continued humping it undeterred, his swinging balls making soft plapping sounds against the wall as he groaned delightedly but while still trying to keep his voice down. It was embarrassing for him to need to release so much cum when he unwantedly got a growth spurt like the one he got a short few minutes ago.

Little did he know, a long-term solution was about to present itself to him.