“reverse / opposite” in Japanese is 逆, read gyaku, saka (ぎゃく, さか). It is a Grade 5 Kyōiku kanji, taught in year 5 of Japanese elementary school, and appears in words such as 逆説 (paradox).
What does 逆 mean?
逆の方向へ歩く。
Same sound, different character — the classic trap. Compare them side by side: