[Samatarou]

I would say it means “summer shade”, since the kanji is clearly used to refer to dim light or shadows. Also summer shade sounds natural and fits the mood of the music, whereas "summer light" sounds kind of weird to me, I'd expect something more like "summer sunshine". Having said that, this theme seems mainly to be played during sunny scenes of Yukito & Misuzu walking along and not when people are sat in the shade.

I've seen this kanji mistranslated before, notably in the ED to the Agatha Christie series where Frothbite translated "shinju no tsukikage" as "pearl moon shadow" instead of "pearl moonlight" (or just "pearly moon"). You can't usually just translate kanji in isolation, the meanings rarely map one-to-one onto English words so you need to consider the context to divine which of a range of English words fits the particular use.