Charao-tachi ni Nanpa → Soku Hame Kamasareta Jimizuma: Otto no Tonari de Netorare 3P Onsen Ryokou

Come on, ma'am, let your husband hear you scream from behind the wall! During a trip with my husband, two womanizers started hitting on me in the private hot springs, and in the end...
(Source: Coolmic)
Note: Simultaneously released in long-strip and traditional formats, with 9 and 3 chapters respectively.