The feature of this Mms.apk is as follows:
1. User-Agent Switcher: Available to select useragent, including "iPhone (3.0)" for Black SIM and "SoftBank MyrMMS" for Silver SIM or any other SIMs
Useragent customised by user him/herself is also available.
2. Emoji support for both Unicode 6.0 and SoftBank's original emoji encoding - (with 471 emoticons)
3. Added ability to change message font size.
You can use at your own risk. I am not responsible for any damages.
You must understand the danger of "UNLIMITED MEASURED RATE OF MONTHLY CHARGE (PAYMENT), NOT FLAT RATE (or dual flat rate)", due to misconfiguration of SoftBank APNs.
For more details, read "this". Information and knowledge that you must understand is included, before you try to use you own handset in Japan.
EXTERNAL DOWNLOAD LINKS
Mms-Android_4.1.2.apk (JB: API Level 16)
Mms-Android_4.0.4.apk (ICS: API Level 15)
For Android 4.2.2, 4.3.1 and 4.4.2, check this out.