STORY2 It's a blessing!
Magic in the penetration stone

Stones collected at the point where the tunnels break through are called penetration stones.

These have been used as a talisman for safe childbirth since ancient times, when Empress Jingu placed a penetrating stone at her bedside during delivery, and a very healthy baby was born (from Kojiki, Japan’s oldest historical record).

Since tunnel construction was very difficult, its success was associated with the overcoming of difficult obstacles and achievement of initial goals. Thus, the penetration stone is also used as a talisman for success.

Because of the danger involved in tunnel construction, a keshogi is placed above the portal of the tunnel before the start of construction to honor the mountain goddesses and pray for safety. The penetration stones are even more full of luck because constructions involve risks.