Star is a cuck, Marco was cucked. There is a significant difference between the two.
Star actively helped Marco hook up with Jackie then tried to include herself in their relationship. Going so far as to hold Marcos hand while he kissed Jackie.
When Star hooked up with Tom, she included Marco AND Kelly in their beach date. There's no way Star was unaware of Kellys recent break up. Romantic beach, two single people. Star knew exactly what she was doing here.
And what does Marco do when he see's Star and Tom kissing? He goes and hooks up with Kelly.
I almost want to say that Marco was being alpha but he was pushed into Kellys arms by Stars actions, actions that cucked not just Marco that day but Tad as well. All according to keikaku.fuck spoilers