Sekijukansei
The phrase 赤受咸青 or “red accepts blue entirely” refers to Kokoro (red) and Satoru (blue). The existence of Kokoro is necessary for Satoru to exist as he does.
By adding the heart/Kokoro (心) radical to each kanji, the phrase becomes 恋愛感情 or “romantic feelings/love and emotion”. A bit forced given the nature of the story, but Uchikoshi was trying to add romance to the game after all.
Remember11 EXPLAINED 