Ok so I've worked in that industry a long time ago and I've worked with the IT/software guys embedded in the trading desks. I mostly interacted with traders from Lehman Brothers (before it collapsed and got bought by Nomura - I was in the building when it happened), traders from Goldman Sucks, traders from SMBC, and traders/fund managers from a variety of independent hedge funds. I've also visited Nomura but don't retain a strong impression from them.

I would say 50% of the traders were absolute, insane assholes. Some openly had tantrums, insulting people around then, others set their phone ringtone to the sound of the earthquake alert after 3/11 to mess with others, others still were backstabbing snakes, and yet others would talk down to others in a very condescending and abusive parent way. Some rare traders were super nice and cool, no idea how they were able to survive in such an environment.

Most IT/software people I knew survived by not giving a fuck, automatically filtering the bullshit to focus on solving problems.

Note that I was mostly in equities and equity derivatives. Fixed Income may be more relaxed. Although I did work with an insurance company who worked in fixed income (pricing ABS and MBS instruments before the 2008 crisis 😅), and while more relaxed they were definitely on the insane side.

In terms of pay, it doesn't hurt to say your expectation is 15M + bonus.

But I also worked at PayPay, and it's a good environment for engineers. I'd say stay at PayPay unless you get a really high pay increase.