https://www.twitter.com/negi_haruba/status/1053501200627200001Apparently, they considered initially giving Ayaneru the role of the five quints, but they scrapped the idea because it was dificult to do, however Negi still wanted her to do a quint and they settled down with Yotsuba, If I'm reading correctly its because she seemed to be the most faithfull in the first commercial.
