I've updated LINE NoLastSeen to v0.5, which supports not to show "Read" for specific users/groups.

And this tweak doesn't hide "Read" for all users anymore, so you should set it enable for the user you want to hide "Read".

Here's the tutorial:

(1) In the talk, click the button on top-right

(2) You'll see a menu like the screenshot below, click the settings.

(3) Then, you can see there's a new button. Click to enable/disable hide "Read" for the user.

P.S.

If you installed "LINE NoLastSeen toggle" (The ControlCenter toggle), chat without individual settings will be show/hide "Read" as the toggle setting.

Otherwise, you can set specific hide/show "Read" without installing the toggle.

UPDATE.

If you want old version of LINE NoLastSeen, please install "LINE NoLastSeen Lite" from Cydia.