At first, I wonder why the dad doesn't have enough savings for old age that the son has to pay for everything. It is a high burden to support 2 elderly and yourself with a bachelor's degree.
But...
The son is 24, which means assuming he is on the normal life route, he only started working when he is 21 or 22.
The dad was 44, the mom was 40 when they have a son. So in a typical Japanese life (depicted in mangas, yes I know it is unreliable) he should be working since 22 and so does the wife. Assuming they got married when the mother is 25 dad 28. Dad has worked for 7 years, mom 3 years, 1/3 of salary is their savings so 3 years worth of savings. Then okay... let's say they are then penniless since they have a wedding and used everything and then the mom quit work immediately. Also...maybe they don't have any inheritance...
Up until the son is born dad work for another 16 years.
The first 16 years (27 to 44) he paid for the house and living cost and fertility treatment so let's say he has like 1/5 of his salary unused, so....3 years worth of savings.
Then the son is born. For 15 years (45-60)he used every penny.
Then the house should be fully paid but he is now retired.
Then he received pension money, how much is it? Let's say it is 1/3 of his original salary.
He has to use that and his remaining savings to raise the kid, keep himself and his wife alive for another 7 years.
So yeah...there is no other choice. The son gotta get through all that. I just wish he had some emotional-support...I am sure if he has someone to talk/complain to he can push through another few years and things will be a bit more stabilized. Like better income or a good way to take care of the parents...
The moral of the story....have some savings and If your salary is so so, find a side business/extra income....LOL