by Rumiko Takahashi Ryoga and Ranma will stay forever young unless they eat a special mushroom at the perfect time. Eat the right mushroom size and your age adds up accordingly! Can the two 'boys' survive their squabbling over not wanting to share being naughty and therefore spanked by Akane and the terror that is 'Uncle' Soun's whiskers until the mushrooms are 16 centimeters tall? T+ Rating.