The protagonist fell asleep during the welcoming party at his part-time job.
When he opened his eyes, the shop manager and his busty senior coworker were having sex!
Even more, he gets a lewd invitation from Yuzu, the female staff member who he secretly has feelings for☆
Sex under special circumstances will take his breath away!

(Source: FANZA)

tl;dr The employees and the owner of a small cafe bar — all in all two men and two women — form two couples and get swept up in group sex shenanigans.

1. Swapping Party!? (スワッピングパーティー！？)
2. Swapping Party!! (スワッピングパーティー!!)

Note: Ch. 1 is vanilla, Ch. 2 contains swinging/partner swapping just as the title says, so consider yourself warned if this is not your cup of tea.