Founded by former PopCap staff, Electric Manta is comprised of mobile game and hypercasual veterans from the likes of Kwalee and Miniclip.
Going forward, Electric Manta will focus on developing casual, hybrid casual, and hypercasual games across its studio operations.
Electric Manta and Sunday are expected to begin testing game prototypes together from December 2021.
"We are a one stop shop for developing casual, hybrid, and hyper games," said Electric Manta founder and CEO Mark Cochrane.
"This helps us manage risk, and at the same time innovate both core and meta gameplay development.
"Electric Manta wants to find core mechanics that everyone loves, and use that to drive the next generation of casual games. The next match three or merge will be created by us, owned by us, and played by everyone."
Sunday managing director Chistoph Sachsenhausen added: "We are thrilled to enter into a partnership with the Electric Manta team who share a common passion to create hit games that everyone can play, with Sunday."
In August, Electric Manta revealed a long-term partnership with hypercasual publisher Voodoo with the aim of extending the lifetime and engagement of hypercasual games.