Pyth, 11 10 bytes
FNwpt`+4CN
Try it! My first go at Pyth.
FNwpt`+4CN
FNw # For N in w (w is input, N will be single char)
p # Print without newline
CN # Int with code point `N`
+4CN # Add 4 to int with code point N
`+4CN # representation of above (basically to string)
t`+4CN # Tail (All but first character)
Python equivalent:
for N in input():
print(end='', repr(ord(N) + 4)[1:], end='')