There are always so many possibilities when a plant suggestion is asked for. Also, not seeing the space, I must fly blind, so to speak.
I prefer strong contrast between plants, so perhaps something like Fatsia japonica, which would visually fill the space with its bold foliage, while still leaving empty space within to avoid overcrowding.
If you were thinking of a more typically bushy shrub, perhaps a Camellia spp. or Spotted Laurel (Aucuba japonica).
Actually, I will lobby for one each of all three suggestions, rather than three of one. Repetition is so over-rated in garden design.