Instead we have the romantic journey of Raku and Chitoge. Onodera and the other girls? They're just created to get in the way and provide spice for that journey. As to the other girls: Well, the author knows who Raku ends up with. To make the other girls believable romantic rivals, he then had to work hard to make you fall in love with those other characters to keep you guessing, and, ideally, fool you.
I sadly agree with you here, pretty much the majority of the female characters in this story were to add up spice to the story.
Now, Onodera's fans will say: "But she's perfect!" Exactly. Yes, she's an Earthly angel, but that's her problem: She's too perfect. In the real world, maybe we pick the rarity of an angel like Onodera, but this is a work of fiction.
Although I LOVE Onodera's character, I wouldn't put her in such high, idyllic pedestal as 'perfect angel'. She had her flaws, but probably many ppl would think she is too good to be true. And. in some cases, they might be right.
OP: You've got it wrong, yet you're close. "Fragile" is the wrong word and concept. You've followed that thread to a logical conclusion, except it's taken you to the wrong destination. It's not about Raku needing to rescue the most fragile of the girls. Take down the deadend you've erected there and your logical conclusion is that Raku is going to marry Chitoge out of sympathy.
Again, when I used the word 'fragile' was by no means to diminish any of the characters, it is really hard to use a correct adjective to englobe Chitoge's personality. Also, I think you're taking my words in a wrong way. To me, there is a huge difference between 'sympathy' and 'love'. Although one can be inside the other and viceversa. I do believe that Raku chose Chitoge because, at the end, he felt love for her. And not out of a gesture of charity. But also not as idyllic or romantic enough to not feel love for Onodera if the right plot circumstances were put together.
No. Chitoge wins because she's imperfect...and hence, the most like a real female of the girls who are in this manga. If there's a stereotype being filled, that's it.
All characters were imperfect, just that those imperfections were blurred by our own biases. imho that is.
Thanks for your great insight of the topic. (´・ω・)b