Well, taking official sources, you could have different variations in Artist based on them, depending on if you take the vocalist, the arranger, the circle, or mixing them together. The circle i question's site seems to bring up an error, so we can't access that now
So firstly there's the Circle's group name, which is Studio "Syrup Comfiture"
Then there's the General Album Artist name used for the album Love=All, which is Syrufit / Poplica*
You can see it on the album jacket and also shown on sites of circles who feature in it, like Aftergrow:
http://aftergrow12.web.fc2.com/
Another option is to use the Arranger/Artist of the song, which is
not Syrufit, but 平茸 (Hiratake) from Aftergrow, who features in this album
Or just the vocals 綾倉盟 (Mei Ayakura)
You could place still place arranger with the vocalist, but placing vocalist with the circle or album artist name would look quite off, and might not be right. But because there is no merge of both the artist and vocalist anywhere, there is no 'ft.' or 'feat.' in the official stuff, so I'm not sure how right it is to do so
Anyway hope some of this information helps in your decision, also don't forget to have Hiratake in the tags at least, if you don't use it! He arranged this after all
