Faster Hongo if we talk about RHP. Mine suspect number one is Banchina- I even made a post kinda connected to it
here.
Base for it is the dig for science what Usopp has, Seraphins' eyes and connection to stars what Yasopp has in his design and Usopp has in his attacks, and that due to one sickness after a normal poisonous mushroom I doubt that he would cut any mushroom as harsh as he did.
And made comic to that idea connected as well,
here.
Probably data from research made on Yasopp was what was given to MADs, but her curiosity was still not fulfilled enough after the split of MADs. So she continued on Usopp.

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The research probably was around how their eyes worked etc.