I have recently noticed 8 is a pretty common number in the manga I have been reading. Like Samurai 8 and Kaiju NO.8 have the number in their title. There are also 8 gyms in pokemon. Like the number 8 seems very important. Is it related to how the number 4 in Japanese sounds like death?
It all comes down to superstition.
4 and 9 are considered "unlucky" numbers because of their phonological resemblance to the words 死 (shi – death) and 苦 (ku – suffering).
7 and 8, however, are considered luckier. 7's luckiness is steeped in Buddhist tradition and folklore. 8, which is written as 八 in kanji, is reminiscent of a strong foundational base, like a mighty sugi or ginkgo tree or a firm architectural feat.