Mikazuchi (円月投) is a special story from DanMachi Volume 7.
One afternoon, in the central garden of the Hearth Mansion, Bell, Welf, and Mikoto were training, with focus on practicing their grappling. Seeing Bell being sent rolling across the grass by Mikoto, Welf was amazed by eastern martial arts, praising Mikoto as he helped the boy. However, she bashfully denied, crediting Takemikazuchi for her education in martial arts.
Bell changed the topic by asking Mikoto what her strongest technique was. She noted that it was a situational matter, but said that, in general, it should be Mikazuchi. Mikoto explained that it was a foreign technique, modified by Takemikazuchi, which had a great power, and was thus granted the name Mikazuchi, derived from Takemikazuchi's own.
Impressed by her explanation, Bell and Welf asked her if she could perform it, which she said she could, noting that only she was capable of successfully learning it. However, she added that the goddess Tsukuyomi had scolded Takemikazuchi for teaching the technique to Mikoto and the others. As she recalled the event, she mentioned it was powerful enough to be sealed. Interested in the technique, both Welf and Bell expressed their desire to see it.
Although surprised, Mikoto agreed to to show it to them when told it would help improve the Familia's ability. After stacking several mats in preparation for it, Mikoto stated that she was ready while Bell nervously wondered why he was the one who was gonna receive it. In the next instant, Mikoto jumped in the air and caught Bell's head in between her thighs, with great agility, leaving his vision blocked by her underwear. In the next moment, Bell's head was slammed into the mats as he loosed a cry.
Mikoto asked Bell about his opinion but was shocked to see he had passed out, saying she thought she had held back. While Mikoto rushed to help Bell, Welf realized why Takemikazuchi was chastised for teaching Mikoto the technique, releasing a sigh as he understood the whole story.