This function replaces the second character of the input string with its subsequent character if the second character is a lowercase alphabet. Otherwise, it leaves the input string unchanged. 

[CODE]:
```python
def function(input_string):
    if len(input_string) > 1 and input_string[1].islower():
        return input_string[0] + chr(ord(input_string[1]) + 1) + input_string[2:]
    else:
        return input_string
```