I think it needs a border, even a very thin light coloured one.

I also think shortening the width of the sig will really help the balance. While I know Ryll loves negative space, there will still be tons of it even if the sig width is reduced, and the focus of the sig will improve as well.

I think adding a very faint glow effect and adjusting the colour of the text a bit will do wonders. The more similar it is to the sakura leaves, the less intrusive it will be.