Extreme summer heat is ravaging Tempest. Rimuru and crew visit a lake they've been told lies beyond the forest, and they change into swimsuits to start having fun... but Shion and Shuna seem dissatisfied with Rimuru's swimsuit. Veldora watches the gang from inside Rimuru's body as he plays a game of shogi with Ifrit. As the Storm Dragon, one who has never experienced swimsuits or water play, he struggles to understand what all the excitement is about...
You guys don't know how it feels to 
have such a capable little sister!
أنتم لا تعلمون كيف يكون الشّعور عند
!امتلاك أخت صغيرة مؤهّلة كهذه
¡No entienden lo que es
tener una hermana tan hábil!
¡No entendéis lo que es
tener una hermana tan hábil!
Vous ignorez ce que ressent
le frère d’une sœur plus douée !
Voi non potete capire come si sente 
un fratello maggiore con una sorella così perfetta!
Vocês não entendem o que é
ter uma irmã tão competente!
Вам никогда не понять, каково это,
когда твоя сестра хороша во всём!