The other guy I mean is Junichi's best friend. (You see him at the very beginning of ep. 8.) In both Haruka's and Kaoru's arc, he, Junichi, and Kaoru are shown as a trio from middle school days. I think a triangle story between them would have been interesting, and I wonder if we won't see Kaoru end up with the best friend in one or more of the other timelines.

I don't have a big problem with the reactions of the other girls in each of these time lines. At the beginning, none of them are that committed to Junichi, and it is just a matter of how the dominoes fall as to which one he ends up with.

In real life, if Haruka has any leanings towards "batting for the other team", the chances are that her marriage with Junichi could be negatively affected in the future. That said, I have known a couple of women in my life who have had sexual relationships with women who nevertheless firmly prefer men (and are now happily married headed-towards-middle-aged moms).

T-Man! Your new avatar looks like Nagi from Hayate no Gotoku. (And I thought you didn't like that show.)