Yesterday's enemies could be today's friends.
From Starfy Wiki
Yesterday's enemies could be today's friends., with variations such as yesterday's enemies could be today's friends and yesterday's enemy is today's friend, is a phrase in linguistical culture and surprise catch phrase by Moe in Densetsu no Starfy 3, as 『今日のテキはあすの今友』.
Moe said the phrase in relation to Ogura; who had passed away, in resentment to Starly who insensitively called him a 'bad guy'. It is known as a deep moment in the The Legendary Starfy series. In Japan, this is also related to 闇 任天堂 (Yami Nintendo), dark or more mature moments in Nintendo video games.