I went and reread all the Milk Morinaga stuff and I gotta say angst and anxiety are themes that run through all her work (except maybe Gakuen Polizei, which I've never finished because it's really not very good IMO). Morinaga-sensei has read a lot of Rumiko Takihashi and she loves to use misunderstandings and peoples' inability to communicate and lack of self-awareness to keep the motors of her series running. I think it feels a little harsher here because the scenario is more grounded and the protagonists are (theoretically) adults. But these two are nowhere near as messed up as the protagonists of, say, The Secret Recipe, who consistently made me want to give them both noogies.
Kisses was a lot better than I remembered it being, but my favorite of hers will probably always be Hana & Hina After School. Hina is maybe my all-time favorite disaster lesbian. Cool beauties who are secretly total dorks are my kryptonite.