Aki has always been so sweet but prefers to not show it. Himeno said that he used to cry whenever the rookies he was looking after died and he tried to protect Denji from the same fate, albeit in a harsh way because he wouldn't have listened otherwise(he still didn't) Hell, he even tried to withdraw his squad from the Gun Devil fight because he was worried about Denji and Power even though fighting the Gun Devil was his only goal in life. Left all of his savings for Denji, Power and Himeno's family too. He didn't deserve that death dammit
