it is completely understandable to be uncomfortable with the sexual assault in dandadan. it's important to discuss how it's framed, whether it's handled poorly, or if it could be been portrayed better. but the number of people - even fans - stating that it is only fanservice, irrelevant, or could be removed is frankly bizarre to for SO many reasons, starting with the fact that this parallel exists.
the anime made it even more obvious by interpolating cuts from the first scene into the second one.
i thought this scene showed that momo gaining her powers by believing in her relationship with her grandmother gives her the strength to fight back against what is basically a horrific, much more aggressive and abstract (maybe even absurd?) representation of her shitty gross ex - who was demanding she 'put out' and pay for the love hotel in very first scene.
while the escalation from one scene to the next is surprising, it's not something that comes out of nowhere. this first scene is meant to be a set-up to what will happen later. it sets the tone, though significantly more lighthearted at this point. it tells you that sex, sexuality, etc. is something dandadan will touch on - though you don't know what the scope and depth will be until later in the chapter.
i cannot recommend this video enough, as it discusses some interesting interpretations of what the serpoians and turbo granny represent in their respective assault scenes, as well as how right now the treatment of both scenes is unfortunately uneven.
more notes about plot and thematic relevance below the cut. spoilers for anime-onlies (up to chapter 8, will probably be covered in episodes 4/5).