Sae-Bom's birthday turns into the happiest day...of Hee-So's life?! After Won-Jun asks her out during Sae-Bom's birthday party, Hee-So's on cloud nine! But is everything really all sunshine and roses? Sae-Bom has had to grow up in the span of a day, Won-Jun is secretly troubled by Sae-Bom's obvious distress, and Whie-Young's magical exertions have kept him out of commission. On the five-day anniversary of Hee-So's relationship bliss (leave it to her to celebrate even the smallest milestones!), she runs into the long-absent Whie-Young en route to school and gets dragged into cutting class with him! But when they return to find Won-Jun waiting for them back at Hee-So's, will her cheating ways (?) lead to an explosive finale for her second chance at love?