There is nothing — not robots, LMDs, a post-apocalyptic future — that will stand in the way of Alphonso "Mack" Mackenzie and Elena "Yo-Yo" Rodriguez's relationship on Marvel's Agents of S.H.I.E.L.D.. Er, except maybe Mack's role as director, and his fear of putting Yo-Yo's life on the line.

In the special video above, Marvel.com had the opportunity to talk to Henry Simmons ("Mack") and Natalia Cordova-Buckley ("Yo-Yo") about what makes their relationship so steadfast despite the hurdle at the start of Season 6. It's not easy being a power couple when the fate of the world is constantly on the line, but this duo makes it look easy.

According to Simmons, "the key that makes Mack and Yo-Yo work is the willingness to die for one another."

"When you love anyone, you wouldn't want to put them out in a situation where they could possibly die," noted Simmons on Mack's decision to keep his distance from Yo-Yo at the start of the season.

"It's part of their growth, and I think it proves to Mack that yeah, Yo-Yo is a firecracker; she's rebellious and all, but in Season 6, we saw her play for the team and vouch for him and defend him and trust him. We see their relationship even stronger, much more grounded than it's ever been," added Cordova-Buckley.

See the strength of Mack and Yo-Yo's relationship as they face Izel in this week's two-hour season finale on Friday, August 2 beginning at 8|7c on ABC!