Set up by former Latitude director Justin Hayward, the agency will provide paid and natural search services for both firms. Make it Rain will also work with sister company Evolving Media, which provides web design and back-office services.
The agency, which began trading on 4 August, has four staff and will focus on helping brands build their online presence.
"We are a small boutique agency, but are dealing with big clients in a different area in terms of advancing their online business, rather than giving just one specialist service," he added.
Hayward was previously strategic development director at Latitude, and worked at Inspired Digital and TBWA Digerati.
"If the online process is put together end to end, you have a much better understanding of a brand's business than if you just offer a search solution," said Hayward. "That's where I see a gap in the market."