Now in episode 1, I'm not sure if Shin or anyone was the heroines boyfriend. However, at the end of ep 2, when she did some kind of time-jump back to August 1 (perhaps due to her untimely fall over the cliff/her death?), it definitely appears like Shin is her boyfriend - I mean, he kissed her like it was nothing, lol! And as Rito2Ru pointed out, she got a "bad end" or simply put, she died or had something untimely happen to her - and each time something like that happens, she jumps back to August 1. When that happens, I think circumstances/situations around her changes as well, like Shin being her boyfriend now, and Orion who was with her in Ep 1 and most of Ep 2 now being gone (or at least it appears that way for now). Also, in ep 2, the "heroine" asks Kento about a vision she had where they were both at a festival. However, Kento doesn't seem to remember - I think that was an event that happened during one of her prior time-loops. In fact, I think a lot of her visions are from prior time-loops.
Also, I think that guy with the green hair might be partly responsible or at least knows something about the "heroine's" amnesia/time-loop thing. In ep 2 when he saves her from getting hit by the car he says "This has happened before, too." - indicating that he prolly saved her before in one of her prior time-loops; he also says "You don't remember me, do you? Of course not." - and since he says "Of course not," I think that means he knows she has amnesia and knows somewhat what's happening to her. Now what I find rather intriguing is that after the green-haired guy walks away from the "heroine" after saving her, her heart "flutters." I wonder if that's supposed to mean maybe she fell in love with him in a prior time-loop? I mean, when he saved her, it seemed they were playing romantic/mystery type of music. I still think though that green-haired guy is up to no good based on the very devious-looking face he displayed in ep 1.

One last thing that I think may be worthwhile to point out, was something in the Opening Intro. In it, there's a part that has all the guys about 1 inch from kissing her (including the guy w/the green hair!!!). Now I don't know if that's supposed to mean anything, but if it does, I think it might have something to do with her time-loop and her sometimes having a different love-interest... but I don't know.

What I thought was hilarious is how Shin can ask the Heroine if she remembers his name, but he doesn't think to ask her if she remembers her OWN name, lol. I mean c'mon, wouldn't that be a question you ask someone if they can't remember anything? You know, maybe that's why Orion doesn't want her to go back to the hospital! Because the doctors might use some common sense and tell us her name!

Yeah, I think it's prolly cuz each time she time loops back to Aug 1, situations around her change as well, and her visions/memories are from her prior time loops.

In fact I think there is a tie-in with all the card suits shown in the series: something like she's a Queen that needs to pick her King. The loops/dimensions will be one per suit, or something like that.