1. Building LibreOffice Korean Community In 2017, I visited Taiwan’s FLOSS Conference, COSCUP(Conference for Open Source Coders, Users, and Promoters) as the Korean FLOSS Contributor. When I attend COSCUP, I met TDF board member, Italo Vignoli, Taiwan’s TDF members, and Japanese TDF members. When I watched, the TDF board member, Italo vignoli’s presentation, I had a strong impression in his presentation. As a result, I'm building LibreOffice Korean Community. I'm talking about my experience of starting a source code contribution[fix Korean Hangul/Hanja dictionary’s bug] and running a community from 2017 to now(2020). This year, I participate as a contribution mentor for the NIPA's contribution event with NIPA[National IT Industry Promotion Agency, IT Industry promotion organization by the Republic of Korea] cooperation. (The event teaches students and the public how to participate in open source activities.) With the help of NIPA, I will participate as a mentor for LibreOffice Korean language contribution and share how to promote LibreOffice in Korea. 2. CJK's common issues and differences LibreOffice is mainly developed by Western European language speakers. So, the CJK issue of LibreOffice is caused by developers who don't understand CJK languages. East Asian cultural sphere, East Asian Countries uses Ideographs(漢字/汉字, Chinese Characters, Mandarin Chinese: hànzì, Japanese: かんじ　kanji, Korean: 한자 hanja). But, Each country and region, Ideographs glyph shape is different in East Asia. Also, some ideographs meaning and sounds are also different. Also, The numeric expressions in Korea, China, and Japan are sometimes similar and different. I will show some common consistency and differences issues between CJK(Korea, China, and Japan) and talk about how to handle and cooperate in LibreOffice. I found some bugs and fixed CJK issues on LibreOffice. I deal with CJK common issues and differences, such as numeric expressions in Korean & Japanese, and don't distinguish both Korean and Japanese fonts from all CJK[Chinese, Japanese and Korean] fonts(such as the Noto CJK font series and Source Han series, etc.), and so on. Because Both Google's Noto CJK font series and Source Han font series is the first open-source "pan CJK(Chinese, Japanese, Korean) typeface, It is not possible to distinguish CJK fonts from the existing Libre office source code. Also, This talk shows the difference of Ideographs in East Asia, such as Mainland China, Taiwan, Hong Kong, Korea, Japan.