Oshima Tomo, of NicoMaki fame (or infamy), used to use the name (or is actually named?) Mitsuki Nikaidou. She also used the pen name Narusawa Meguru.
Nikaidou Mitsuki's credited with being Oshima Towa's "partner" (相方... read into that what you will) and helping her a lot with her manga - not exactly an "assistant" in the regular sense because she seemed to do a lot more than an assistant would. You can definitely see the art style similarity, particularly if you look at Tomo's earlier solo releases, probably because she's had to draw like Towa for a long time!
Sweet Pea is Tomo's circle, and Cocoa Break is Towa's circle. They used to do some releases together, to the extent that they share an artist category on Tora no Ana, but nowadays they make a distinction between the two. Possibly because Tomo apparently likes to draw a tonne of lesbian porn and Towa doesn't seem to. XD
They live together! You can see the photos of their cats on their Twitter. Tomo's kitty, Potechi, is the cutest. And I've read some blog articles in Japanese where people HAVE confirmed that they are two different people, having seen them both in person together.
... I swear to god I didn't go and stalk them for a few hours one day... I mean... Why... Would ... I have done that...
Marvellous, thank you for the answer.
Don't worry, I wouldn't judge if you were a stalker because, I...sometimes...I mean...it's just so... tempting to know...