Kouhou Mimamori Osananajimi ga Ama Sugiru

Natsuki Mashima is 24 years old. Every guy she's dated is a total loser... she has absolutely no luck with men. Among her friends, there's one guy she can classify as a nice guy: her childhood friend, Shouya Sano, two years younger than her. Unlike his former self, who was spoiled and lonely, Shouya has evolved into a caring, overly talkative, "motherly" guy, and today, he's once again taking care of her...!?

(Source: Comic Walker, translated)