A one-byte change starts at one leaf.
Only chunk C changes
The original C chunk is 0xcc. The changed chunk is 0xcd.
C:0xcc→0xcd
The C leaf changes
With this toy one-byte hash, changed C hashes to 0xcd.
H(cd)=0xcd
The other leaves stay put
A, B, and D are unchanged, so their leaf hashes still read 0xaa, 0xbb, and 0xdd.
A,B,D unchanged
Summary
The changed leaf is C=0xcd.