The following article contains spoilers for Chainsaw Man. To catch up on the latest chapter, it's available as a physical copy, or can be read online at Viz Media.
It makes sense why a young man so starved of affection his whole life would want someone to fill the gap. Usually for those around his age, he'd look for that in a love interest. And although Denji is certainly not bad-looking, there exist people out there that want to take advantage of him.
But the world is a melting pot of good and evil. Part of growing up is having encounters with multiple types of people, and Denji has a lot of growing up to do. So what exactly can be said about Denji's various love interests in Chainsaw Man?
Makima
The woman who "saved" Denji. In his eyes she is an angel, so much so that the 3rd end credits show her in a divine light from Denji's perspective. She's particular about what she expects from him, and is rather assertive - one of Denji's favorite traits in a woman. Not only that, but she gave him a place to stay, a job, clean clothing, and food. Given his life up until now, she's everything that he never got. Anime-only watchers may feel the same way, and see her as a flirty woman who just likes to tease her subordinates. She is fairly unique personality, and it's not very common for such a character, let alone a woman supervising such an important division - especially in the 1990s.
As the story progresses, we steadily notice there's something "off" about Makima. She was never conventionally "normal" to begin with, but she became Denji's first manipulative "ex", for lack of a better term. He developed a reliance on her and in turn, she used him for her own interests. Makima essentially created a world around Denji that he could find a place in, before ripping it all away - making herself the only person he could turn to. Needless to say, she's not a good person and definitely not the ideal "first girlfriend" most boys dream of, even if she and Denji weren't official.
Verdict: She's too old for you
Power
Power and Denji don't have a very romantic relationship, instead more so an awkward sibling relationship. While he finds Power attractive, it doesn't take long for the two to butt heads. Upon their first meeting, she makes a deal with Denji that if he's able to retrieve her cat, she'll let him feel her up. Denji, being the idealist he is, takes her up on that offer - though when the opportunity finally arises, he's sorely disappointed at how underwhelming it is.
Soon after she moves in with him and Aki, Power starts making noise and mischief of her own. Ironically, she acts similarly to how Denji did upon first arriving. Overtime, the two (as fans like to say) share a single brain cell and soon enough, the two become every parents' worst nightmare when left to their own devices. Despite having bathed together at one point, and even shared a bed, Power became the sister he never had.
Verdict: Dating your sister is weird
Reze
Reze is a Russian foreigner around Denji's age and manage to bond with him pretty well upon their first meeting. When they both break into a school to show Denji what the inside of one looks like, she plays the role of the teacher in one of the classrooms, in which she teaches him how to write various vulgar phrases and slang. Because they are so close in age, their senses of humor overlap pretty well. Additionally, Reze also offers to teach Denji how to swim, a skill he never had the opportunity to learn. It's a pretty wholesome dynamic in the sense that most of their time spent together is just simple wandering off, going on dates, seeing the fireworks, visiting her at work, etc. It's the ideal "first love".
Unfortunately, while it can be argued that Reze genuinely cared about Denji, the sole reason she was in Japan in the first place was to kill him. When their battle comes to a draw, Denji offers her the opportunity to run away with him, as his time spent with her was still precious to him. The next day, despite their differences, she decides to take him up on the offer - but got ambushed by Makima before she had the chance.
Verdict: Never date a girl you just met
Asa
Asa is one of Denji's classmates when he finally gets the chance to go to school. His experience with women may be mixed, but that won't stop him from wanting to find The One. Asa certainly notices him and knows of him, but his identity as Chainsaw Man isn't common knowledge in his new environment. Her arc has yet to be concluded, but Asa poses as a potential love interest, and her stern personality may be just what Denji needs to whip him in shape. The fact that she's sharing a body with a devil may make things a bit more complicated, though.
Verdict: Let's hope she isn't two-faced