How many cases do you know where one of the supporting female characters grow to mind blogging popular, that she evolves to main character, then to main love interest status?
Pic rel is Tsurara from Nurarihyon no Mago, she destroyed the original human love interest in popularity, to the point the author just bent the knee and had Tsurara win the bowl at the end, a Yokai girl despite the entire theme of the series was about the coexistence of humans and yokai.
Closest I can think of is Mikoto Misaka. Well except maybe the love interest part.
Probably the classic example is Mary Jane Watson from Spider-man, but that isn't manga so probably doesn't count.
Botan. Also the big tits from demon is a part timer, but that was the author's decision influenced by the anime, I think.
Getting her own series is better than being relegated to be the love interest.
Does Hinata from Naruto count? In the manga she had no presence whatsoever, meanwhile the anime introduced a train of fillers with Hinata in; that definitely influenced her growth in popularity, and people who seriously thought she could win Naruto's heart were committed to see it through, and in the end it happened, causing one of the greatest shipping butthurt I've seen.
That has always been Kishomoto's intention.
Botan didn't win the Yusuke bowl though, although the Chiho example from Maou-sama definitely applies, the only case that I can think of where a girl with the Magical Baby plot on her side actually lost the race to someone else, Emi got fucked over hard.
I mainly remember that for being a case of the main girl losing, yet even the people who usually root for main girls to lose got upset over said ending.
The classic one, Lum was a huge cunt early in the manga, that acted more like Shampoo from Ranma, the clear loser, than the more subdued and charming alien girl that really managed to become the main love interest.
How about a case where the author didn’t bent the knee out of spite? She definitely knew why anyone gave two fucks about this manga when it was running, Ebino was scoring lead color pages left and right.
Now nobody remembers Hatsukoi Zombie ever existed, while meme’ing about her newest work Boy’s Abyss which got more popular for all the wrong reasons.
This. You look at the early episodes, it's clear Rumiko intended Lum to be the villain who constantly came between Shinobu and Ataru. But Lum became so popular, she displaced Shinobu and it became the series we all know. When Rumiko did Ramna 1/2, it was clear she wasn't going to let history repeat, and every time Shampoo started softening or becoming sympathetic there'd be a hard reset and Shampoo would go back to being evil.
She did win, but was she popular? More people seemed to be surprised and butthurt about the fact than those who were happy.
Tomoya after story is the canon route and everything else is fan fiction, i don't care.
How could that have been influenced by the anime? Emi was the clear favorite of everyone. Did he do it to spite fans for some reason?
I'm sure Chihirofags loved her winning, but I think Wakaki making her win did long-term harm to his career. His next few series after TWGOK (including King of Idol) were axed. The mobage he was writing for, Baton Relay, was also very short-lived. He has a new manga right now and last I heard it was doing okay, but I think he switched magazines for that.