If one were on the lunar near-side (the side that eternally faces the Earth due to tidal locking), then wouldn't the Earth always be visible in the sky day and night? More importantly, what is Kaguya doing there? The Lunarian capitol is on the far-side of the moon.

Flargon said:
wouldn't the Earth always be visible in the sky day and night?

It would. The Earth would undergo shifting phases like we observe with the moon, so a 'new Earth' may not be readily visible due to the lack of reflected sunlight and the sun outshining it. The fact that it's nighttime on the moon matches up correctly with the 'full Earth' in the picture. It's interesting to point out that a moon day and moon year are both one Earth month.