Both are romance dramas about high school students with more serious/melodrama vibes.
+ two MLs pursue the FL
+ ML is more rough around the edges and aggressive while the SML is reserved, kind, soft
+ [SPOILER] FL ends up with the reserved ML
Orange Soda is a purely contemporary drama while Love Alarm has a sci-fi aspect.
Both are youth dramas in which the FL is childhood friends and in love with the ML who ends up getting into trouble over and over. Meanwhile another boy moves into her street and begins being kind to her and eventually becomes the endgame.
Both are mini-series that take place in high school and follow a low-key FL who is more an avenue to explore the ML and SML's characters than a strong character in her own right.
+ love triangle, both ML and SML fall first
+ both ML and SML help/protect the FL in various situations
+ intense rivalry between MLs; one is known as a troublemaker while the other is more reserved and laid back
Orange Soda has a more serious tone while Best Mistake stays light and surface-level.
Both are romance dramas set in high school.
+ love triangles with intense rivalry between ML and SML
+ second lead syndrome
+ tragic friends-to-enemies backstory (btw FL and ML in OS, btw ML & SML in TB)
+ FL is a more reserved character who doesn't want attention