I guess with both Project and I not really needing to eat, Kaito decided to improvise with the serving? I should have been suspicious when Kaito was waiting the table...

Alternate theory by  thatwhichji :
So Sl invites SL to a dinner date, but what he doesn't know is SL is also seeing SL, and made other plans to see SL there, so SL and SL are eating when SL bursts in, furiously demanding to know what's going on, so SL SL and SL are caught in a love triangle while Kai tries to leave and not have to deal with this.
Also SL and SL are ALSO secretly lovers and just haven't told anyone

Drawn by   KaitoFletcher