Long, long ago, a kind-hearted old woodcutter climbed into the hills every morning to gather firewood among the pines. When noon arrived, he sat down on a mossy tree stump high on the slope and unfolded the bamboo wrapper holding the plump white rice balls his wife had lovingly shaped for his lunch. A gentle mountain breeze rustles through the green bamboo grove while birds sing high in the branches overhead.

Before he could even take a bite, one round rice ball slipped from his fingers — korori, korori — and tumbled straight down the steep hillside. The game's tall grid is that very slope: whenever a rice ball wild lands, it rolls down its reel and turns every cell along its path into a wild. Watching a single rice ball tumble all the way down the slope brings the playful rhythm of the old folktale to every spin.

Instead of stopping in the grass, the rolling rice ball dropped — suttonton! — right into a little mouse burrow beside the old tree roots. When the woodcutter knelt down on the hillside to peer inside, he heard tiny voices singing a cheerful tune from deep underground: “Omusubi korori, suttonton!” The cheerful rhythm of their underground song echoes up through the roots, inviting the curious woodcutter to follow.

Leaning closer to listen to the song, the old man lost his footing on the moss and tumbled down the hole himself. On the reels, a mouse burrow catches any rice ball rolling from above, and landing enough burrows on the finished board opens the doors to the mouse palace below. Stepping through that tiny burrow transforms the quiet mountain hillside into a bustling festival beneath the earth.

At the bottom of the tunnel stood a grand underground palace where grateful mice in festive coats were pounding mochi with wooden mallets and singing in the woodcutter's honour. In the game, their lantern-lit hall comes to life as a classic wooden pachinko parlour framed like a street-corner paper theatre. Warm paper lanterns and festive banners line the timber walls as the mice welcome their guest to the grand hall.

The old man drops his rice balls one by one into the brass pin field, watching each ball clatter and bounce toward the nine prize pockets at the bottom — or into the two side tulips that add extra rice balls to the queue so the run keeps going. Every bounce against the gleaming brass pins keeps the suspense alive until the rice ball finally settles into a pocket.

Whenever a bouncing rice ball drops straight into the central kakuhen tulip, red lanterns flare across the palace hall: extra reel spins are awarded on the spot and the multiplier ladder climbs a full rung, boosting the payout of every rice ball that falls afterward. The festive music grows livelier with every rung climbed on the ladder, filling the underground hall with golden light.

Right beside the centre pocket sits the mice's parting gift to the kind old woodcutter — a woven treasure basket brimming with gold koban coins. Climbing to the top of the multiplier ladder and dropping a rice ball into that basket crowns the folktale with its richest reward. Just as in the beloved fireside story, a simple act of kindness on the hillside leads to an overflowing basket of gold.