Akachan to BokuBaby & Me - Ragawa, Marimo

Takuya is a normal Japanese elementary student whose mother died not very long ago, leaving him alone with his father and his baby brother Minoru. But his father is a busy man, and Takuya has to look after Minoru. Because of this responsibility that would normally never burden a child of his age, Takuya sometimes resents his fate and his baby brother... but his love for Minoru gives him the strength to carry on.

(Source: ANN)
Included one-shots:
Volume 2: Time Limit
Volume 4: Secret Boy ni Tee Dasuna!!
Volume 6: Baka de Karukute Wagamama de
Volume 15: Natsu to Kimi no Irradiation

Aka-chan to Boku was published in English as Baby & Me by VIZ Media under the Shojo Beat imprint from February 7, 2006 to February 2, 2010.