Is this a sequel???

Yes, look:

Kuroneko Series Timeline
1 Kuroneko Kareshi no Asobikata - Shingo & Keiichi's Love begins.
2 Kuroneko Kareshi no Amaekata - A Lover's Quarrel
3 Kuroneko Kareshi no Nakasekata - Move to live together as a couple
4 Kuroneko Kareshi no Aishikata - Interfered by Arrogant Bro, WereLeopard Clan Leader
➽ 4.1 Fukigen kareshi no Nadamekata (Side Story) - Big Bro x Caretaker Eli
5 Kuroneko Kareshi no Afurekata - Shingo's opponent appears.
6 Kuroneko to Kareshi to Ouji - "Shingo, pls look after me~" said puppy-eyes Rio.
➽ 6.1 Fukigen kareshi no Saraikata (Side Story) - Eli & Jin travel to save his cousin Sara.
7 Kuroneko Kareshi no Arukikata - Shingo re-encounters a Calico Cat, Kokonoe.
8 Wagamama Ouji wa Neko wo Karu - Adult Rio seeks for lover assembles Shingo

Spin off