Garbled character (mojibake) inside the icon in the user menu for Japanese names

I am brand new to nextcloud.
(disclosure: I have used owncloud, so it was easy to install and set up.)

But I am having trouble displaying Japanese character inside the icon in the user menu. (also in the login icon, after logging in)

Please look at the attached picture.

For example, the 3rd user paXX (パXX) should have pa(パ) displayed inside the icon (circled red).
The 4th user tsuruXX (鶴XX) should have tsuru(鶴) displayed inside the icon (circled red).
Same for all users with Japanese names.

oc_accounts table shows correct encoding.

mysql> show create table oc_accounts;
| Table | Create Table |
| oc_accounts | CREATE TABLE oc_accounts (
uid varchar(64) COLLATE utf8_bin NOT NULL DEFAULT ‘’,
data longtext COLLATE utf8_bin NOT NULL,

Also, the ‘value’ of data field in the oc_accounts seems correctly encoded.
For example, “\u30d1” is katakana pa (パ).
“\u9db4” is kanji tsuru (鶴).

Could someone please give me some guidance?

I have one instance of owncloud running in the same server (CentOS 6.9) with the same php (5.6) and same mysql (5.5), but owncloud displays those names inside the icon correctly.