Symuri's Favorite

What is the purpose of Yuyu with Nana?
If it weren´t because it is a super shoujo I would think the manga would become a yuri twisted or shoujo-ai...
I admit to being rather badly thought out, but since I don´t understand Yuyu, she's the character that interests me the most.

I really didn't expect this to turn kinda psychological when I started this....

This manga is like a manga rendition of my life if it had someone to save me from it like Nana does. My Yuyu ended up not wanting to be my friend anymore which granted me my freedom. I didn't cut my hair as to get away from her though, I changed my favorite color to orange instead. Luckily I don't have another Yuyu in my life as of right now so hopefully Nana is able to get rid of her like I was able to get rid of my friend that was like Yuyu.