Missile Happy! Series by Miki Kiritani

Mikako has a sister-complex so strong she won't let just any man wed her sister. On an undercover investigation to learn more about the newest bachelor, she ends up moving in with him! And thus begins an angsty, hilarious story full of misunderstandings, wackiness--and even love!

Mikako, our over-zealous heroine, has a sister-complex so strong she won't let just any man wed her sister. On an undercover investigation to learn more about the newest bachelor, she ends up moving in with him. And thus begins a hilarious series full of misunderstandings, wackiness, and every other shojo cliche you can think of, including love.

It's been about a year since Rou and Mikako have been living together. Even though New Year's is coming up, lately Rou's been so busy with school and work that he's left Mikako alone. Mikako is trying her best to support him but has mixed feelings about his work. On top of that, Rou has started to change his attitude around her. Mikako doesn't know why but trusts and supports him in every way! Will her thoughts reach Rou or have they already?