The function takes a string input and returns a new string where some characters are replaced with their adjacent character.

[CODE]:

```python
def transform_string(s):
    result = list(s)
    replace_dict = {'c': 'b', 'o': 'n', 'e': 'd', 'i': 'h', 'u': 'y', 'r': 'q', 'r': 'q', 't': 'u'}

    for idx, char in enumerate(result):
        if char in replace_dict:
            result[idx] = replace_dict[char]

    return ''.join(result)
```