Posted: Today at 00:55
I have to say it doesn't look to be in brilliant health, Yensid. The gray coloured main stem has died back and needs to be pruned off, just above the point where the red side branch appears, or the die back may continue down and kill off that good (red coloured) branch.
The other problem is that the root stock (many acers are grafted) has sprouted from the base and those different coloured (green) stems are from the type of tree used as the rootstock and will take over completely if left.
The problem now is to decide whether to remove the growth from the rootstock so that all the energy goes into the main tree or not. It's a tricky one as the main tree may be too far gone and die anyway, then you'll be left with nothing. If you keep the basal growth, it will dominate and the remaining (red-coloured) branch will eventually die off but may last a few more years.
The good news is that japanese acers are usually grafted onto acer palmatum rootstock, so if you leave the green branches to grow, you will still have an acer!