How is Sam so skilled at kissing

"Huh? Weren't we going to your place? Why are we here?" Mia asked, puzzled.

After leaving the hospital, they didn't head straight to Sam's house but stopped at the supermarket closest to Sam's apartment instead. 

Mia had initially planned to do "that thing" at Sam's house. After all, going to a hotel seemed too strange, even though a lot had happened in her dreams, and it seemed inevitable that her relationship with Sam would turn ambiguous.

But she couldn't let go of her own reservations. For a woman, no matter what her status, it wasn't appropriate to make such a suggestion outright. 

Fortunately, Sam quickly realized the best approach. But why did he seem so natural about it? It was as if the nervous one was Mia herself.

It was strange. Mia was older than Sam, so why did she act so immature around him? And why did they end up at the supermarket first? 

Could it be to buy some condoms? No way... What was he thinking? Could he be...