How about soft, gentle, vulnerable, open, risky?
I chose "risky" because Clark is allowing Lois into one of the most private and personal areas of his life, a place his parents don't even know about. He's chosen to open one of the hidden places in his heart, and the risk is that Lois won't like it or that she might not understand how vital it is for him to have a place like that.
Fortunately she seems to fully comprehend what he's offering her. She doesn't have a comparable physical place, but she can extend her trust in him even further and accept the trust he's given her to safeguard this most precious of places.
Beautiful, touching, tender, revealing, and any number of other adjectives which would apply. Excellent vignette. And placing it in the middle of the honeymoon is perfect. Thank you for sharing this with us.