I did go through something similar for quite a while and I didn't realize how much I hurt my friends and my partner with the words i've been saying to convey my feelings for several months now.
At some point my friends where asking a lot of questions and truly sit us down to talk. I made my partner and my friends cry with my words which i didn't expect. And only after my partner confessed she thinks I will break up with her (even though we've been together for 7 years and planning to marry ), did it dawn on me. My friend also just frankly saying that I'm being extremely pessimistic and unfair kinda did it too. It broke some kind of downward spiral i was on.
It also took a lot of pushing from me to get my partner to be honest and telling me her true uncomfortable worries. I was really pushy and by yuri commenters standards it would be called toxic and over the line for not backing down. it was the first time that i heard her say anything like that for a very long time and it reset my brain. I really needed her to be honest to me and I wasn't capable to settle down with anything less.
I genuinely couldn't realize that by putting myself down I put the people closest to me down as well. But also my partner needed to learn to be honest, that your partner deserves honesty even if its uncomfortable.
I feel like the manga wants to convey this kind of story. I dont know where it begins to be toxic but it took "not supporting my convictions" and "being pushy" to get to a better place. (also therapy would be really nice lol)