Tsuki to Himawari

From Serenus-Dreamers:

After losing their parents, Fumino and her brother hop from one relative to another. Getting tired of all those moves, she finally decides to quit school and work to support her brother on her own. As they sat on a park bench, her teacher appears in front of her and agrees to her demands of marrying and supporting both her and her brother!! Is he serious or just playing around...?!

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Also contains the oneshot, Tsukio to Himawari, in vol. 1.
Asahi-kun is a carefree junior-high student, never attaching to girls even though he enjoys going with them. But when the school's number 1 honor student Mitsuki "cyborg" Konno asked him to a 1-month date, in exchange for the front row ticket to his favorite singer's concert, he was forced to accept. He only has to show her what it feels like to date, right? He is ready for that...however, what he's not prepared for was his heart's reaction...