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When transform to anothersection, color masking effect

Hello, Nice to meet you.
I need some help for color masking effect.
Please see this website.

I want to make this site homepage. But I have some problems on that.
Please see this video.

As you see on that video and screenshot, sample semi circle shape have color masking effect when transform to another section.
Please help me on that.
thank you your help.