Some all carbon knives have a very highly reactive cladding (iron or carbon steel) that can leave that iron taste and discolor things like onions.
Takeda's never did that for me, and with the new Takeda's being stainless clad I would worry about it even less. With only a very small exposed carbon core (Aogami Super in this case), you don't have to worry about just that carbon core doing that. AS itself is not typically (I've never seen it do it) going to do this, and with so little exposed the worry is essentially obsolete.
Hope that helped.
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