Maybe the female OC is a vampire hunter who initially mistakes Yui for a vampire. As they get to know each other, they realize they have a common goal of trying to survive in the world of Diabolik Lovers. They could form a strong bond and face the challenges of the vampire world together, like dealing with the various schemes of the different vampire clans.
One idea could be that the female OC is a new student at the school. She has a special power that she doesn't fully understand yet. Yui befriends her, and together they try to figure out the secrets of the Sakamaki brothers. The OC's power might attract the brothers' attention in different ways, some being more menacing and some being more curious.
If you want the clearest chapter reference, go to Chapter 57. Early on, Lu Xingchao's numerous fans were stunned.; later, the chapter leans on Holy shit, what's up with God L?.
If you want the clearest chapter reference, go to Chapter 106. Early on, Thinking of this, He Yun nodded with a hint of anticipation.; later, the chapter leans on Alright, then tell me my fortune, what do I need to do?.
Look to Chapter 109 for the clearest answer. It begins with And another thing," Jiang Li said, taking out a tissue to wipe her lips,..., keeps building through The next time we have a meal, don't try to chat with me unless you're fine..., and lands on [You're indeed more likable than me, the type.
If you want the clearest chapter reference, go to Chapter 68. Early on, Jiang Li carried the noodles straight out of the kitchen and came to the...; later, the chapter leans on Uncle had already returned from the fields, and he was sorting through a....
A practical answer is Chapter 78, because it turns the idea into a concrete scene. The chapter opens with He Yun, too, tidied up and walked over to rest in the shade of a tree., adds pressure through That weed whacker is obviously mine!, and ends on [HAHAHA, is it just me or does Movie Emperor He.
The best chapter pointer here is Chapter 81, ""Chicken Fleeing and Crabs Escaping" cp". It opens with Qi Tianyu, who chose curry beef rice, received a piece of curry and a... and closes on The summer on the Southwest Plateau is no joke; the sun at three o'clock....
The best chapter pointer here is Chapter 44, "Laozi's Hands Are Made to Drive a Ferrari!". It opens with But the next move by the production team proved they hadn't forgotten the... and closes on Does anyone here know how to drive?.
If you want the clearest chapter reference, go to Chapter 60. Early on, What's with Jiang Yan, treating his own sister Jiang Li like this?" "He...; later, the chapter leans on When Jiang Li found a place to live, she didn't bother with him either,....
If you want the clearest chapter reference, go to Chapter 73. Early on, Director Sun, tongue-tied, finally managed to squeeze out a sentence,...; later, the chapter leans on But isn't it due to your production team's lack of consideration?.
If you want the clearest chapter reference, go to Chapter 106. Early on, Thinking of this, He Yun nodded with a hint of anticipation.; later, the chapter leans on Alright, then tell me my fortune, what do I need to do?.