Rena is a classmate of
Keiichi's. She is quite interested in his everyday life, possibly because of an inherent urge to look after people.
She comes with the standard-issue honesty, earnesty and blushes that you find in many heroines.
However, her only reward for taking care of Keiichi is an incessant series of pranks. It really is unfortunate for her.
She likes anything and everything she considers adorable, and this is also a very typical trait in a heroine.
But that is also her greatest weakness...
(spoiler hidden)[Edited from
Rena Ryuugu on 07th Expansion Wiki]