The term “New Religion” refers to any religious group in Japan that has its roots after the Meiji Restoration of 1868. This includes the Nichiren Buddhist organization Soka Gakkai, as well as the infamous Aum Shinrikyo. The latter probably explains Saito's concern.
Hamburger: In Japan, hamburgers can be served in a bun, called hambāgā (ハンバーガー), or just the the patties served without a bun, known as hambāgu (ハンバーグ) or “hamburg,” short for “hamburg steak.” The type mentioned by Saito was the version without the bun. (ハンバーグ)
Rooms in Japan are measured jō (畳), which is the number of tatami mats required to cover the floor. A tatami mat is 90 cm by 180 cm for an area of 1.62 m2 each. Twelve jō is slightly more than 19.5 m2 or almost 210 square feet.
Alvíss was a dwarf in Norse mythology who was turned to stone through Thor's trickery.
Vestri is a dwarf in Norse mythology representing West.
In Norse mythology, Frigg (Eddas) or Frigga (Gesta Danorum) was said to be “foremost among the goddesses,” the wife of Odin, queen of the Æsir, and goddess of the sky.