Retainer Level?

[Len]

Originally we had envisioned a variety of content for retainers, but we held off on them and kept retainers as they are currently. In version 2.0, we are planning to expand their uses beyond just the current bazaar system, as well as raising their levels and the things they can do. However, we do not have any plans of linking the inventory slot numbers to their levels, so leveling them up will not yield a greater amount of inventory space.

Thanks for the information, Rukkirii!