Note:
(a) "According to mythology, the volcanic rock – officially called Sessho-seki – is home to Tamomo-No-Mae, aka the Nine-Tailed Fox. The demon apparently took the form of a beautiful woman, who was part of a plot to kill Emperor Toba 鳥羽], ruler of Japan from 1107 to 1123."
(i) Sessho-seki 殺生石
(A) Kanji 殺 has three Chinese pronunciations: satsu, sa-i (Japanese does not have a diphthong), and setsu.
Kanji 生 has two Chinese pronunciations: se-i and shō.
The kanji has three Chinese pronunciatinsL seki, shaku and koku, the last being limited to ancient salary of a government official as a unit of grain.
(B) The second syllable of setsu in 殺 is skipped with a syllable-length of silence, as in 殺生石, it (skip) is noted with duplication of the next consonant -- here the "s."
(ii) Tamomo-No-Mae 玉藻前: She did not exist in history. Legend has her, having transformed from the Nine-Tailed Fox 九尾の狐, killed by 三浦 義明（1092年-1180年）. 三浦 and 鳥羽 were real.
(b) "Located in the mountainous northern region of Tochigi, near Tokyo, the rock is something of a tourist hotspot"
(i) The stone is located at 栃木県 那須郡 那須町の那須湯本温泉付近. 栃木県那須町 = Nasu Machi, Prefecture of Tochigi. The tochi 栃 is Japanese horse-chestnut, native to Japan and whose seeds contains irritants to gastrointestinal system. Horse-chestnut is quite far from chestnut in relatedness.
(ii) Japanese-English dictionary:
* yu-moto 湯元; 湯本 【ゆもと】 (n): "source of a hot spring"
* Kanji 湯 mans hot water, nath or hot spring -- but not soup (in Japan).
* sui-so 水素 【すいそ】 (n): "hydrogen (H)"
(c)The ja.wikipedial.org for 殺生石 says: "殺生石付近一帯は硫化水素、亜硫酸ガスなどの有毒な火山ガスが絶えず噴出しており、「鳥獣がこれに近づけばその命を奪う、殺生の石」として古くから知られた名勝であった。"
My translation: The stone is close to toxic volcanic gas such as 硫化水素 hydrogen sulfide (化学式 H2S; 水素 is defined in (b)(ii) ) and 亜硫酸 sulfurous acid (化学式 H2SO3, whose salt is sulfite; not ot be confused with sulfuric acid H2SO4, whse salt is sulfate) that is spewed out incessantly 絶えず. If 鳥獣 come close, they die -- hence the name 殺生の石.
Which explains that the cracked stone is yellowish inside, omdocatomg presence of sulfur.