“to return / to give back” in Japanese is 返, read hen, kae (へん, かえ). It is a Grade 3 Kyōiku kanji, taught in year 3 of Japanese elementary school, and appears in words such as 返事 (reply).
What does 返 mean?
本を図書館に返す。
Same sound, different character — the classic trap. Compare them side by side: