逻辑性和连贯性分析：

原文主要涉及到两个问题，一个是关于购买可以在日本使用的上网卡的问题，另一个是关于购买随身WiFi的问题。然而，两个问题之间缺乏逻辑上的联系，段落之间的连贯性较差。

改进后的原文：

根据您的描述，您计划去日本参加一个为期19天的交流项目，并且您使用的是OPPO手机，支持移动4G网络。您想知道是否可以购买一个在日本可以使用的上网卡，以及是否可以购买随身WiFi。

关于购买上网卡的问题，您可以考虑前往360商城购买360随身WiFi。目前有3代和2代两种型号可供选择，分别售价为24.9元和19.9元。360随身WiFi是一种可以插入电脑并生成WiFi信号的硬件产品，您需要安装360免费WiFi电脑版驱动软件，然后可以一键生成WiFi热点，供您的手机和其他设备免费上网。

另外，您还可以考虑使用360免费WiFi这款手机蹭网软件。该软件可以帮助您搜索附近的WiFi热点，并一键连接免费的WiFi热点，从而开始免费上网。您可以通过分享热点获得金币，也可以通过签到获得金币。金币可以用于兑换流量和时长，时长可以连接三大运营商的公共热点。当其他人通过360免费WiFi连接您分享的热点时，您也可以获得金币。

由于您将在日本使用手机，建议您咨询当地的手机营业厅或联系OPPO客服，了解是否需要开通国际漫游功能或者手机是否支持国外的4G SIM卡。

改进后的原文（英文翻译）：

According to your description, you plan to go to Japan for a 19-day exchange program, and you use an OPPO mobile phone that supports mobile 4G network. You want to know if you can buy a SIM card that can be used in Japan and if you can buy a portable WiFi device.

Regarding the purchase of a SIM card, you can consider buying a 360 portable WiFi device from the 360 online store. Currently, there are two models available, the 3rd generation priced at 24.9 yuan and the 2nd generation priced at 19.9 yuan. The 360 portable WiFi is a hardware product that can be inserted into a computer to generate WiFi signals. You need to install the 360 Free WiFi PC version driver software, and then you can easily create a WiFi hotspot for your phone and other devices to access the internet for free.

In addition, you can also consider using the 360 Free WiFi software, which is a mobile app that helps you search for nearby WiFi hotspots and allows you to connect to free WiFi hotspots with just one click. You can earn coins by sharing hotspots or checking in. These coins can be used to exchange for data or internet access time. With the internet access time, you can connect to public hotspots provided by the three major network operators. When others connect to the hotspots you shared (via 360 Free WiFi), you can also earn coins.

Since you will be using your phone in Japan, it is recommended that you contact the local mobile phone service provider or OPPO customer service to inquire about the necessity of activating international roaming or whether your phone supports foreign 4G SIM cards.