How to handle data loss during merge

Question

Here's my data on first table

Id     City        Count
1      New York      445
2      London        543
3      Tokyo         342
4      Jakarta       646
5      Tokyo         454
6      Singapore     340
7      Jakarta       293
8      Tokyo         219
9      Singapore     478

Here's my data on second table

City         City_code
New York             1
London               2
Tokyo                3
Jakarta              4
Singapore            5

Then, I try to merge

df_c = pd.merge(df_a, df_b, on="City_code")
df_c

And the result

Id     City        Count   City_code
1      New York      445           1
2      London        543           2
3      Tokyo         342           3
4      Jakarta       646           5
5      Tokyo         454           3
7      Jakarta       293           5
8      Tokyo         219           3

As you can see, the singapore city data is loss during merge, how to handle that?

Notes:

1. My Actual dataset is 1568 rows
2. when I perform pd.merge(df_a, df_b, on="City_code", how='outer') the data being 1570 rows
3. when I perform pd.merge(df_a, df_b, on="City_code") the data being 1546 rows