If i play Temporal Breach on Ekko, Ingenious do I pay for the additional cost stating the following: As an additional cost to play me, return a friendly unit to its owner's hand.

Correction on the unit you have to bounce as additional cost. It is not restricted to the BF you replay Ekko at.

**Yes — you still pay it.** Temporal Breach's "ignoring its cost" only zeroes out Ekko's printed Energy and Power costs; it does nothing to additional costs (Rule 356.1.b.1), and Ekko's is a *mandatory* additional cost, not a "you may" (Rule 356.2.a.1). You must return a friendly unit you control to its owner's hand as Ekko is played back, or you can't legally finalize him — in which case the play is undone and he stays in banishment (Rule 358.5; FAQ #3434 covers this exact "ignore its cost vs. additional cost" split). One thing to watch: Ekko himself is in banishment while this happens, so he can't be the unit you bounce — you need a different friendly unit in play. This can change what the subsequent showdown looks like.