Minor Spoilers for Ryoma's character. Be cautious.

When Gonta discovered that Ryoma's looking for a reason to live, he began to introduce Ryoma to all of his favorite bugs so that he would have some friends. At first, Ryoma just played along because he knew Gonta was trying to be helpful. But eventually, he took over babysitting duty whenever Gonta couldn't tend to his bugs. Calls them by name and talks to them and everything.