Wasn't there a time skip at some point early on? Was it just getting Ding Yi to a slightly more appropriate age, or was it retconned, or does anyone remember what happened there?
I think it's her EX. The one before Yi and the one that smashed her heart at university
I realize that "Two Spirals" is the official English title, but just to point out: らせん is more properly translated as "helix," as in 二重らせん, a double-helix.