A continuation of Yuuta x Mayumi's story in Kodomo wa Tomaranai.
This is the third in a series of stories:
1. Mainichi Seiten
2. Kodomo wa Tomaranai
3. Children's Time
4. Kodomo no Iibun
5. Isoganaide.
6. Hanaya no Nikai de
Although not specifically "sequels", this is the order that the stories were written/published in.

Based on the novel Mainichi Seiten!

From Juné:
A typical summer night turns hotter than usual at the Obinata household when a stranger named Shuu Asuou turns up and announces that he’ll be living with them from now on! Shuu explains that he has married their sister Shima and that he shall stay at the house while awaiting her return. But when she doesn’t turn up, he proclaims that he is there to stay for good! What is Shuu's motive for wanting to be with Obinata family? Read this heartwarming and hilarious manga to find out!

Mainichi Seiten series:
Vol 1-2 Mainichi Seiten
Vol 3-4 Kodomo wa Tomaranai
Vol 5 Children's Time
Vol 6-7 Kodomo no Iibun
----Aki-chan no Iibun
Vol 8 Isoganaide
Vol 9-10 Hanaya no Nikai de

This time, the focus is on the second eldest brother in the family from Mainichi Seiten — the bespectacled Akinobu who wakes up one morning in an unfamiliar bed with someone most familiar and unexpected.
Mainichi Seiten series:
Vol 1-2 Mainichi Seiten
Vol 3-4 Kodomo wa Tomaranai
Vol 5 Children's Time
Vol 6-7 Kodomo no Iibun
----Aki-chan no Iibun
Vol 8 Isoganaide
Vol 9-10 Hanaya no Nikai de

This is the fifth in a series of stories:
1. Mainichi Seiten
2. Kodomo wa Tomaranai
3. Children's Time
4. Kodomo no Iibun5. Isoganaide.
6. Hanaya no Nikai de
Although not specifically "sequels", this is the order that the stories were written/published in.

Atsushi, an ex-chef, Torajirou, a high school baseball player, and Nakagawa, a famous ex-composer (all 3 losers in life) started up a Convenience Agency. Then, as if fate had a hand in it, Nakagawa once again crosses path with Takahashi, an incredibly talented young composer, when a job that needs Takahashi's expertise arises, rocking the three's otherwise quiet life towards a whole new direction. From making you laugh to moving you to tears, this is a story of love and peace, and the world as seen by losers.

from Forever More

A short extra story about Akinobu and how he reacts to the incident which happened in Kodomo no Iibun

Mainichi Seiten series:
Vol 1-2 Mainichi Seiten
Vol 3-4 Kodomo wa Tomaranai
Vol 5 Children's Time
Vol 6-7 Kodomo no Iibun
----Aki-chan no Iibun
Vol 8 Isoganaide
Vol 9-10 Hanaya no Nikai de

This is the fourth in a series of stories:
1. Mainichi Seiten
2. Kodomo wa Tomaranai
3. Children's Time4. Kodomo no Iibun
5. Isoganaide.
6. Hanaya no Nikai de
Although not specifically "sequels", this is the order that the stories were written/published in.

Continuing on the story of the Obinata household, the focus this time is on the two youngest members, Yuuta and Mayumi.
This is the second in a series of stories:
1. Mainichi Seiten2. Kodomo wa Tomaranai
3. Children's Time
4. Kodomo no Iibun
5. Isoganaide.
6. Hanaya no Nikai de
Although not specifically "sequels", this is the order that the stories were written/published in.