Go as in the board game. Either way, the date is a pun: go is usually said as igo in Japanese. i(1) go(5).

There is a theory that kishimen noodles were originally shaped like go stones, which would explain their name!

Kishimen → kishi men(noodles). The argument here is seemingly that the kishi comes from 碁石 (goishi; "go stone") → 碁子 (goshi) → 棊子 (kishi).

I can reach victory in the next move on 8 different positions! Talk about a difference in reach! The original pun was with both "reach" (e.g. the reach of a sword) and "立直" (a term that apparently comes from mahjong and means "being one step away from victory") having the same pronunciation in Japanese.

In gomoku, the player who plays as black (the first player) is forbidden from making a double three (placing a stone in a manner that creates simultaneously two or more groups of three), a double four (placing a stone in a manner that creates simultaneously two or more groups of four) and an overline (making a line of six or more stones)! Gomoku (gomoku narabe in Japanese): something akin to connect 6, but in a go board, and requiring only 5 stones in a row. The rules described above are for renju, one of the rulesets for gomoku.

Gomoku (if you line up 5 stones, you win)

Ghost-Half-chan, who kept on placing stones wherever it was easy