Some sort of yes answer summary
What Suikama is sitting on is kinda relevant
He could be assisted in getting off what he was sitting on
He had some sort of connection/bonding with it
He can survive without sitting in it
His age has partial relevance in helping us find the answer
Two crimes were involved
The second crime got someone killed
Suikama was a victim of the crimes
Suikama is currently dead, from the second crime
The first crime occured when he was a baby/child
The first crime was committed intentionally
The first crime left Suikama with injuries to his legs
The second crime was likely with the intent of murder
The second crime was a long time after the first
Suikama was kidnapped in the first crime
There is a reason for why Suikama is sitting even when he can walk
We need to find out how he was kidnapped and how his legs were injured
He suffered internal damage that affected his legs
Was what he was sitting on relevant to the kidnapping?
Was he used as a test subject for something during the kidnapping?