The Dolphin in the Little Mermaid (2020)

Both are mini dramas with childhood friends to (slight) romance.
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The main couple are childhood friends/playmates who now have a distance between them (due to their age gap vs. one's popularity), despite the ML's crush on the FL which the FL is unaware of. Both MLs are very popular while the FLs are not. Each episode opens with a cute clip of the two as children getting into mischief.

Both are short dramas in which the main couple, now in high school, were childhood friends who've drifted apart. Both dramas have flashbacks to their childhood.

Both dramas have a main couple who are childhood friends, now in high school. In both dramas, the ML falls first and harbors a crush for a long time on the FL without her realizing.

Both dramas have a main couple who are childhood friends, now in high school. In both dramas, the ML falls first and harbors a crush for a long time on the FL without her realizing.

Both are short stories about childhood friends with a dash of romance, a trio friendship/triangle, and an open but mostly happy ending.

Both are mini dramas with a school setting and a trio friendship (two guys, one girl) that began in childhood and now has a hint of romance between the girl and one of the guys.