This time let's talk a bit deeper about romance; to be specific it's about love rivals.
The idea came from the word 'villain'. It is obvious how love rivals can turn into 'villain's. What do you think of them? What kind of love rivals do you like or hate? Do you think it is necessary to make a shoujo or josei series interesting? Or maybe you have special views regarding love rivals?
Talk it away!
For me it depends on the type of love rivals. For example, I like Fuka's and that-little-celebrity-whose-name-I-forget's role in Kodomo no Omocha as love rivals of the two main characters. They come natural; their 'dirty play' are also natural and not in annoying level. But when I read The Bride of the Water God, in other case, I feel like there are too many love rivals coming one after another and they always play dirty while the main casts are just too dense to realize it. Kind of annoying. ^^;
A rival is by no means necessary but can add a nice bit of tension to romance manga, if done well. Kurumi is one of my favorite characters in KimiToo; with such well mannered, kind protagonists she added some nice sour notes to the story. The challenge Kurumi presented helped Sawaka better understand herself and what she really felt for Kazehaya. The romantic side of Ouran was better for having Hikaru as a friendly rival for Haruhi's feelings.
There are many good romance manga without major rivals. High School Debut had no rival character, and was all the better for it. Puppy love and jealousy don't really mix. Lovely Complex had a rival but he was only a brief challenge, Risa and Ootani was to great a pairing for a rival. As far as I am concerned a rival is only as good as the writing. As nothing more than a trope, rivals are worthless. But a rival that uncovers emotions the lead character never thought they had adds a lot to a story.